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- 1 Analytische Chemie; Referenzmaterialien (1815) (entfernen)
Paper des Monats
- ja (22)
Isotope analysis is a tool for material research. For example, it may provide information about the provenance of a sample or changes in dynamic systems. Here is presented optical spectroscopy as an analytical alternative to mass spectrometry for isotope quantification based on the isotopic shift of atoms and diatomic molecules.
Calcium isotope analysis can be an important tool for paleoclimate studies of the carbon cycle, as well in carbon capture technology, but its utility is limited by challenges using conventional mass spectrometry. We propose a new fast, precise, and high-throughput technology based on multiple complementary high-resolution spectroscopies analyzed by machine-learning.
Wie lässt sich die Herkunft von Rohstoffen, Lebensmitteln oder Umweltschadstoffen einfacher, schneller und kostengünstiger als mit bisherigen Methoden bestimmen?
Die Dissertation zeigt auf, dass man das grundlegende physikalische Prinzip einer Isotopverschiebung mit in Adlershof entwickelten Optik-Instrumenten für die Herkunftsbestimmung nutzen kann. Die entwickelte Methode ermöglicht es in Zukunft den Ursprung von Rohstoffen, Lebensmitteln oder Umweltschadstoffen kostengünstiger und wesentlich schneller bestimmen, als dies mit bisherigen Methoden möglich ist.
Kann man das grundlegende physikalische Prinzip einer Isotopieverschiebung mit einem Optik-Instrument für die Herkunftsbestimmung nutzen? Carlos Abad hat eine wegweisende Methode entwickelt, die es in Zukunft ermöglicht den Ursprung von Rohstoffen, Lebensmitteln oder Umweltschadstoffen kostengünstiger und wesentlich schneller bestimmen, als dies mit bisherigen Techniken möglich ist.
Advances and Applications of Molecular Absorption Spectrometry: from Non-Metals to Isotope Analysis
(2020)
The present work covers two main aspects of high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS-GFMAS), an analytical technique for elemental trace analysis.
First, a comprehensive mechanistic study of molecule formation in graphite furnaces is presented, which is a key step into the recovery of analytical signals. For this, the molecule formation of CaF was studied, which is used for the indirect analytical determination of fluorine in HR-CS-GFMAS. A zirconium coating catalyzes the CaF formation, and its structure was investigated. The kinetics of this reaction was established by monitoring its molecular spectrum at different atomisation temperatures. An Arrhenius plot showed a pseudo-first order reaction with respect to fluorine (n = 1). An intermediate state was isolated, and its structure was elucidated by spectroscopic methods: scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XANES and EXAFS), and Raman microspectroscopy. Here a mechanism is proposed, where ZrO2 works as a heterogeneous catalyst: after a pyrolytic step, an intermediate state of ZrO(OCaF) is activated, and at higher temperatures, CaF(g) is released from the zirconium-coated graphite surface.
Second, analytical methods were developed by using HR-CS-MAS as detector for non-metals and isotope analysis. Therefore, the determination of organic absorbable chlorine in water, the quantification of fluorine in consume care products with declared perfluorinated ingredients, and the determination of sulfur content in crude oils were investigated. Finally, the high resolution of the instrumentation allows to measure isotopic shifts with high precision in some observed molecular spectra. Consequently, the molecular spectra of enriched isotopes of boron and magnesium were investigated, establishing so the potential of HR-CS-MAS for the accurate and precise determination of isotopic amount ratios.
Der Bunsen-Kirchhoff-Preis 2022 wurde am 23.06.2022 anlässlich der analytica conference in München an Dr. Carlos Abad verliehen - in Anerkennung seiner exzellenten Entwicklungen im Bereich der continuum source atomic absorption spectrometry (CS-AAS).
Dr. Carlos Abad ist ein herausragender Experte auf dem Gebiet der Atom- und molekularen Absorptionsspektrometrie. insbesondere trug er maßgeblich zur substanziellen Weiterentwicklung von Echelle-Spektrometern für die CS-AAS bei. So gelang es, einen quantitativen Zugang zu Elementen wie Bor, Chlor, Fluor und Schwefel, mittels AAS zu erreichen. Erstmals demonstriert Dr. Carlos Abad am Beispiel eines Zr-Modifier, dass durch die Zeitauflösung der eingesetzten Echelle-Systeme mechanistische Untersuchungen zur Wirkung des Modifiers im Graphitrohrofen möglich sind.
Besonders hervorzuheben sind seine Arbeiten zum Einsatz der CS-AAS für die Analyse von Isotopen, die eine Genauigkeit aufweist, welche an die der Multikollektor-induktiv gekoppelten Plasma-Massenspektrometrie (MC-ICP-MS) heranreicht. Damit ergeben sich völlig neue Einsatzmöglichkeiten für technologisch hochrelevante Applikationen, wie z.B. die Untersuchung der Alterung von Lithium-Batterien oder die Lithium-Analyse in Blutserum.
Is it a parmesan cheese from Italy? Who painted the Mona Lisa? The determination of the place of origin is essential for consumer protection, detection of falsifications, and also to bring justice.
All the tangible possess an isotopic fingerprint. However, current technologies are too expensive. We work on the development of fast and low-cost optical instruments and methods for isotope analysis.
Isotope analysis can be used to determine the age and provenance of geological samples. Modern techniques in optical spectrometry allow us a stand-off isotope analysis. This seminar will discuss how planetary science with the next Moon and Mars missions drive optical spectrometry into precise and accurate isotope analysis and how BAM will contribute.
Is it a parmesan cheese from Italy? Who painted the Mona Lisa? The determination of the place of origin is essential for consumer protection, detection of falsifications, and also to bring justice.
All the tangible possess an isotopic fingerprint. However, current technologies are too expensive. We work on the development of fast and low-cost optical instruments and methods for isotope analysis.
Glow discharge optical emission spectroscopy (GD-OES) is a technique for the analysis of solids such as metals, semiconductors, and ceramics. A low-pressure glow discharge plasma is applied in this system, which ‘sputters’ and promotes the sample atoms to a higher energy state. When the atoms return to their ground state, they emit light with characteristic wavelengths, which a spectrometer can detect. Thus, GD-OES combines the advantages of ICP-OES with solid sampling techniques, which enables it to determine the bulk elemental composition and depth profiles. However, direct solid sampling methods such as glow-discharge spectroscopy require reference materials for calibration due to the strong matrix effect.
Reference materials are essential when the accuracy and reliability of measurement results need to be guaranteed to generate confidence in the analysis. These materials are frequently used to determine measurement uncertainty, validate methods, suitability testing, and quality assurance. In addition, they guarantee that measurement results can be compared to recognized reference values. Unfortunately, the availability of certified reference materials suited to calibrate all elements in different matrix materials is limited. Therefore various calibration strategies and the preparation of traceable matrix-matched calibration standards will be discussed.
Machine learning is an essential component of the growing field of data science. Through statistical methods, algorithms are trained to make classifications or predictions, uncovering key insights within data mining projects. Therefore, it was tried in our work to combine GD-OES with machine learning strategies to establish a new and robust calibration model, which can be used to identify the elemental composition and concentration of metals from a single spectrum. For this purpose, copper reference materials from different manufacturers, which contain various impurity elements, were investigated using GD-OES. The obtained spectra information are evaluated with different algorithms (e.g., gradient boosting and artificial neural networks), and the results are compared and discussed in detail.
Isotope analysis can be used to determine the age and provenance of geological samples or to study dynamic systems like Li-ion batteries. Modern techniques in optical spectrometry allow us a fast and slow-cost isotope analysis. These techniques include high-resolution continuum source molecular absorption spectrometry (HR-CS-MAS) and laser ablation molecular isotopic spectrometry. This seminar will discuss our recent work on precise and accurate isotope analysis of boron, magnesium, and lithium with geology, climate, and energy research applications.
Simultaneous multielemental analysis of crude oils by high-resolutions absorption spectrometry
(2019)
When crude oil arrives at a refinery it needs a lot of processing before it is suitable for cracking into lighter fractions. Sulfur has to be extracted to meet ultra-low sulfur legislation for most of the fuel grades, and desalination is a crucial process as chlorine within salts is corrosive to refinery equipment. Measuring the amounts of sulfur and chlorine within crude oil is the first step in a complex clean-up process.
Heavy metals, such as vanadium, nickel and iron need to be removed too. These metals can poison the catalyst used to crack the oil into lighter fractions. This is costly as it reduces the useful life of the catalyst. Like chlorine, heavy metals also have a corrosive effect on the plant. There is some evidence that the presence of some metals in the final product can reduce performance.
A fast determination of elements and size of suspended particles is vital for diagnosis and safeguard of refinery equipment. However, sample preparation for current analytical methods consumes precious time and lost particle size information.
High-resolution continuum source graphite furnace absorption spectrometry (HR-CS-GFAS) is proposed as a fast analytical method for elemental determination in crude oils and potentially for simultaneous multielement and particle size analysis. This HR-CS-GFAS instrumentation is coupled to a modular simultaneous echelle spectrometer (MOSES) and provides a full optical window with high resolution (from 180 to 900 nm with bandwidth λ/170,000). By using this set-up, it is possible to generate a multiparameter 3D spectral image (atomic and molecular lines, isotopic shift, atomization delay, and intensities). The generated spectral images can be analyzed by multivariate regressions for the elemental and particle size analysis. Additionally, if several atomic and molecular lines are simultaneously measured, they may be used in multi-energy calibration (MEC), a method based on the use of many wavelengths of the same absorbing/emitting entity to improve the accuracy in analytical atomic spectrometry. This MEC approach combined with multivariate image analysis allows the quantification of selected elements (Si, Al, Ni, Fe, V, S, and Cl) and overcomes matrix effects.
Isotope analysis plays a critical role in various disciplines, including environmental science, archaeology, and forensic investigations. Traditional methods such as mass spectrometry provide precise isotopic data but often require complex, costly setups and extensive sample preparation. As an alternative, optical spectrometry has emerged as a versatile and less invasive technique. This presentation explores the advancements and applications of optical spectrometry methods in isotope analysis, emphasizing their benefits and challenges.
Lithium (Li), Boron (B), Nitrogen (N), Magnesium (Mg), and Calcium (Ca) are pivotal elements across various spheres such as the hydrosphere, biosphere, and lithosphere, significantly impacting (bio-) geochemical and physiological processes. These elements exhibit stable isotopes with substantial roles in geological, environmental, and biological studies. The traditional method for measuring isotope amount ratios has been through mass spectrometry, which, despite its accuracy, comes with high operational costs, the need for skilled operators, and time-consuming sample preparation processes.
Combining optical spectroscopy with chemometrics introduces an innovative, cost-effective approach by the hand of high-resolution continuum source atomic and molecular absorption spectrometry (HR-CS-AAS and HR-CS-MAS) for the analysis of isotope ratios in Li, B, N, Mg, and Ca. By analyzing the atomic or molecular absorption spectrum of the in-situ generated cloud of atoms of diatomic molecules (e.g., Li, BH, NO, MgF, CaF) during the electronic transition from the fundamental state, this method allows for the rapid determination of isotope ratios directly from sample solutions without the need for complex sample preparation.
For each element, the respective atomic or molecule's absorption spectrum was deconvoluted into its isotopic components using partial least squares regression or machine learning algorithms. Robust calibration models were developed, calibrated with enriched isotope, and validated against certified reference materials. Spectral data underwent preprocessing to optimize the modeling to determine the optimal number of latent variables.
The findings showcase that this optical spectrometric method yields results that agree with those obtained via inductively coupled plasma mass spectrometry (ICP-MS), offering a promising, cost-effective, and rapid alternative for isotope analysis with precisions as low as ± 0.2‰. This approach is a significant advancement in analytical chemistry, providing a new way to study isotope variations in biological, environmental, and geological samples.
What does GD-OES reveal about the aging and manufacturing processes of lithium-ion batteries?
(2024)
Glow-Discharge Optical Emission Spectroscopy (GD-OES), a powerful analytical technique, sheds light on the two critical aspects of lithium-ion batteries (LIBs): manufacturing and aging 1, 2. We optimized cell production in manufacturing by adjusting parameters, including cathode doping, electrolyte concentration, and pressing force. GD-OES provided in-depth elemental composition and homogeneity analysis, which is crucial for identifying optimal manufacturing conditions. These findings were validated by electrochemical impedance spectroscopy, confirming the quality of the manufactured batteries.
Shifting the focus to aging, we use GD-OES for fluorine depth profiling, a key element in understanding polymer and electrolyte degradation. However, fluorine presents analytical challenges. We addressed this by substituting argon with a neon:argon mixture, which significantly enhanced fluorine detection sensitivity. This advancement not only improves accuracy but also holds the potential to guide sustainable and cost-efficient manufacturing strategies.
Through its versatility, GD-OES has proven to be a powerful tool for not only optimizing LIB manufacturing processes but also gaining deeper insights into their aging mechanisms. This research extends beyond academic interest, offering tangible benefits for the industry by translating into improved battery quality, extended lifespan, and overall performance.
Magnesium is a naturally occurring element that can be found in several mineral forms in the earth crust. This element presents three stable isotopes 24Mg, 25Mg and 26Mg with a natural abundance of 79%, 10%, and 11% respectively. It is due to their relatively large mass difference (~8% between 24Mg and 26Mg) that isotope fractionation leads to slight isotope amount ratio variations n(26Mg)/n(24Mg) in biological and geological samples. Traditionally, isotope amount ratios have been measured by mass spectrometric methods. However, drawbacks of these methods include the high costs for instruments and their operation, experienced operators and elaborate chromatographic sample preparation which are time-consuming. Recently, optical spectrometric methods have been proposed as faster and low-cost alternative for the analysis of isotope ratios of selected elements by means of high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS-GFMAS) and laser ablation molecular isotopic spectrometry (LAMIS). For the determination of Mg isotope amount ratios, the molecular spectrum of the in-situ generated MgF and MgO molecules were studied. In the case of HR-CS-GFMAS, the absorption spectrum was recorded for MgF for the electronic transitions X 2Σ → A 2 Πi and X 2Σ → B 2Σ+ around wavelengths 358 nm and 268 nm respectively. In the case of LAMIS, it was studied the MgF molecule for the electronic transitions A 2Πi → X 2Σ as well as the MgO molecule for the electronic transition A 1Π+ → X 1Σ around 500 nm. The MgF and MgO spectra are composed by the linear combination of their isotopic components or isotopologues: 24MgF, 25MgF, and 26MgF for the MgF and 24MgO, 25MgO, and 26MgO for the MgO (F is monoisotopic, and the isotope composition of O is assumed as constant). By HR-CS-GFMAS the analysis of Mg was done by deconvolution of the MgF spectrum by a partial least square regression (PLS) calibrated with enriched isotope spikes. The isotope amount ratios in rock samples with and without matrix separation were analyzed. Resulting delta values were obtained with precisions ranging between 0.2-0.5 ‰. On the other hand, LAMIS allows the direct analysis of solid samples with the extended possibility of in-situ analysis. Main advantages, limitations, and scopes of both optical techniques are going to be discussed and compared with MC-ICP-MS.
Magnesium is a major element in the hydrosphere and biosphere and plays important roles in (bio-) geochemical and physiological cycles. Mg has three stable isotopes, 24Mg, 25Mg and 26Mg. It is due to their relatively large mass difference (~8% between) that isotope fractionation leads to slight variations of isotope amount ratios in biological, environmental and geological samples. Traditionally, isotope amount ratios are measured by mass spectrometric methods. Their drawbacks include the high costs for instruments and their operation, experienced operators and elaborate time-consuming chromatographic sample preparation. Recently, an optical spectrometric method has been proposed as faster and low-cost alternative for the analysis of isotope ratios: high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS-GFMAS).
For the determination of Mg isotope ratios in selected rock reference materials, the high-resolution molecular absorption spectrum of in-situ generated MgF molecule was studied applying multivariate analysis and the results compared with MC-ICP-MS. Samples were dissolved by acid digestion and Mg isotopes analyzed with and without matrix. The absorption spectra were recorded for MgF for the electronic transition X 2Σ → B 2Σ+. The MgF spectrum is described as the linear combination of their isotopic components or isotopologues: 24MgF, 25MgF, and 26MgF. The isotope analysis was done by deconvolution of the MgF spectrum by partial least square regression (PLS). A PLS model was built and calibrated with enriched isotope spikes and certified reference materials. Spectra data was preprocessed by a derivate of second order and venetian blinds cross-validation was employed for finding the optimum latent variables. Finally, the model was refined by a genetic algorithm which identified the best subset of variables for a precise and accurate regression. Results are compatible with those obtained by MC-ICP-MS with an accuracy of ± 0.3‰ with uncertainties ranging between 0.02 to 0.6‰.
Mass spectrometric Methods MC-ICP-MS and TIMS) are without doubt the working horse of stable isotope analysis. However, drawbacks of these methods include the high costs for instruments and their operation, experienced operators and elaborate chromatographic sample preparation which are time consuming.
Optical spectrometric methods are proposed as faster and low-cost alternative for the analysis of isotope ratios of selected elements by means of high-resolution continuum source molecular absorption spectrometry (HR-CS-MAS) and laser ablation molecular isotopic spectrometry (LAMIS). First, stable isotope amount compositions of boron (B) and magnesium (Mg) were determined based on the absorption spectra of in-situ generated heteronuclear diatomic molecules (MH or MX) in graphite furnace HR-CS-MAS. The use of a modular simultaneous echelle spectrograph (MOSES) helps to find the maximal isotope shift in the diatomic molecular spectra produced in a graphite furnace by using isotopic spike solutions. Isotopes of boron (10B and 11B) were studied via their hydrides for the electronic transition X 1Σ+ → A 1Π. The spectrum of a given sample is a linear combination of the 10BH molecule and its isotopologue 11BH. Therefore, the isotopic composition of samples can be calculated by a partial least square regression (PLS). For this, a spectral library was built by using samples and spikes with known isotope composition. Boron isotope ratios measured by HR-CS-MAS are identical with those measured by mass spectrometric methods at the 0.15 ‰ level. Similar results were obtained for a multiple isotope system like Mg (24Mg, 25Mg, and 26Mg), where isotope shifts of their isotopologues can be resolved in the MgF molecule for the electronic transition X 2Σ → A 2 Πi. Finally, the application of molecular spectrometry via emission by LAMIS is compared and discussed.
Following fluorinated drugs by molecular absorption spectrometry – from cancer cells to body fluids
(2018)
Fluorine has been widely introduced into pharmaceutical drugs. Due to the high C-F bond strength, a single atom substitution with fluorine produces drastic desirable and tunable changes in the molecular properties. However, the clinical monitoring of these drugs is not straightforward.
Organofluorine compounds are elusive for a non-targeted analysis; a significant problem in fluorine determination is the lack of suitable detection techniques. Standard atomic absorption and emission spectrometers cannot access fluorine, because their resonance lines lie in the VUV spectral range below 100 nm. In the case of conventional inductively coupled argon plasmas (ICP), the plasma energy is too low to generate a significant population of excited fluorine atoms. Recently, our group introduces high-resolution continuum source absorption spectrometry (HR-CS MAS) as a new way for the indirect monitoring of fluorinated compounds. Main benefits of HR-CS-MAS includes low limits of detection, complete analyte recovery, simple to no sample preparation, and short time analysis.
Society for Applied Spectroscopy (SAS) Atomic Section Student Award.
Magnesium is a major element in the hydrosphere and biosphere and plays important roles in (bio-) geochemical and physiological cycles. Mg has three stable isotopes, 24Mg, 25Mg and 26Mg. It is due to their relatively large mass difference (~8% between) that isotope fractionation leads to slight variations of isotope amount ratios in biological, environmental and geological samples. Traditionally, isotope ratios are measured by mass spectrometric methods. Their drawbacks include the high costs for instruments and their operation, experienced operators and elaborate time-consuming chromatographic sample preparation.
Recently, optical spectrometric methods have been proposed as faster and low-cost alternative for the analysis of isotope ratios of selected elements by means of high-resolution continuum source molecular absorption spectrometry (HR-CS-MAS), and laser ablation molecular isotopic spectrometry (LAMIS).
For the determination of Mg isotope ratios in selected rock reference materials, the molecular spectrum of the in-situ generated MgF and MgO molecules were studied and their results compared with MC-ICP-MS. By HR-CS-MAS, samples were dissolved by acid digestion and Mg isotopes analyzed with and without matrix. The absorption spectrum was recorded for MgF for the electronic transitions X 2Σ → A 2 Πi, and X 2Σ → B 2Σ+. In the case of LAMIS, we investigated the MgF molecule for the electronic transition A 2Πi → X 2Σ, as well as direct analysis by the MgO molecule for the electronic transition A 1Π+ → X 1Σ. The MgF and MgO spectra are described as the linear combination of their isotopic components or isotopologues: 24MgF, 25MgF, and 26MgF for the MgF and 24MgO, 25MgO, and 26MgO for the MgO. The isotope analysis was done by deconvolution of the MgF spectrum by partial least square regression (PLS) calibrated with enriched isotope spikes. Results were accurate with precisions ranging between 0.2 ‰ and 0.8 ‰ (2 SD, n= 10) for HR-CS-GFMAS. No statistically significant differences were observed for samples w/o matrix extraction. On the other hand, LAMIS allows the direct analysis of solid samples with the extended possibility of direct analysis, however the precision is lower due the lack of solid isotopic calibration standards.
Boron and Magnesium present two and three stable isotopes respectevely. It is due to their relatively large mass difference (~ 10%) that isotope fractionation leads to considerable isotope amount ratio variations in the nature. These have been used as a proof of provenance of mineral and biological samples, to estimate a contamination source and to the determination of geological processes by erosion or subduction. Additionally, boron is employed in the nuclear industry due to the capability of its isotope 10B to thermal-neutron capture and therefore 10B enriched boric acid solutions are used in the cooling system of thermonuclear facilities and in the alloying of steel and carbides for protective shielding. Traditionally, isotope ratio variations have been determined by mass spectroscopic methods.
Here an alternative faster and low cost method for isotope ratio determination is proposed: high-resolution continuum source molecular absorption spectrometry (HR-CS-MAS). Isotope amount ratios have been determined by monitoring the absorption spectrum of boron monohydride (BH) for boron and Magnesium monofluoride (MgF) for magnesium in a graphite furnace HR-CS-MAS. Bands (0→0) and (1→1) were evaluated. Partial least square regression (PLS) for analysis of samples and reference materials were applied. For this, a spectral library with different isotopes ratios for PLS regression was built. Results obtained are metrologically compatible with those reported by mass spectrometric methods. Moreover, a precision and accuracy of the method of ± 0.5 ‰. This accuracy and precision is comparable with those obtained by thermal ionization mass spectrometry (TIMS) and multiple collector inductively coupled plasma mass spectrometry (MC-ICP-MS) for boron isotope ratio measurements
We propose an alternative faster and low-cost optical method for isotope analysis: high-resolution continuum source molecular absorption spectrometry (HR-CS-MAS).
Stable isotope amount composition of X = Li, B, Mg, Ca and Sr were determined by monitoring the absorption spectra of their in situ generated mono-hydrides (XH) in graphite furnace HR-CS-MAS. Isotopes of boron (10B and 11B) were studied via their hydrides for the electronic transition X1Σ+ → A1Π (Fig. 1a). The spectrum of a given sample is a linear combination of the 10BH molecule and its isotopologue 11BH. Therefore, the isotopic composition of samples can be calculated by a partial least square regression (PLS). For this, a spectral library is built by using samples with known isotope composition. Results with an accuracy of 0.15 ‰ are metrologically compatible with those reported by mass spectrometric methods. Similar results are obtained for n isotope systems like Mg (24Mg, 25Mg, and 26Mg), where isotope shifts of their isotopologues can be resolved as shown in Fig.1b. The extension of this methodology to other elements like Li, Ca and Sr is discussed.
Advances and Applications of Molecular Absorption Spectrometry: from Non-Metals to Isotope Analysis
(2019)
The present work covers two main aspects of high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS-GFMAS), an analytical technique for elemental trace analysis.
First, a comprehensive mechanistic study of molecule formation in graphite furnaces is presented, which is a key step into the recovery of analytical signals. For this, the molecule formation of CaF was studied, which is used for the indirect analytical determination of fluorine in HR-CS-GFMAS. A zirconium coating catalyzes the CaF formation, and its structure was investigated. The kinetics of this reaction was established by monitoring its molecular spectrum at different atomisation temperatures. An Arrhenius plot showed a pseudo-first order reaction with respect to fluorine (n = 1). An intermediate state was isolated, and its structure was elucidated by spectroscopic methods: scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XANES and EXAFS), and Raman microspectroscopy. Here a mechanism is proposed, where ZrO2 works as a heterogeneous catalyst: after a pyrolytic step, an intermediate state of ZrO(OCaF) is activated, and at higher temperatures, CaF(g) is released from the zirconium-coated graphite surface.
Second, analytical methods were developed by using HR-CS-MAS as detector for non-metals and isotope analysis. Therefore, the determination of organic absorbable chlorine in water, the quantification of fluorine in consume care products with declared perfluorinated ingredients, and the determination of sulfur content in crude oils were investigated. Finally, the high resolution of the instrumentation allows to measure isotopic shifts with high precision in some observed molecular spectra. Consequently, the molecular spectra of enriched isotopes of boron and magnesium were investigated, establishing so the potential of HR-CS-MAS for the accurate and precise determination of isotopic amount ratios.
Zusammenfassung
Die vorliegende Arbeit befasst sich mit zwei zentralen Aspekten der High-Resolution-Continuum-Source-Molekülabsorptionsspektrometrie mit Graphitrohrtechnik (HR-CS-GFMAS), einer Analysetechnik für elementare Spurenanalyse.
Der erste Teil der Arbeit umfasst eine mechanistische Studie zur Molekülbildung auf Graphitoberflächen. Dies ist ein wichtiger Schritt, um analytische Signale zu entdecken. Dazu wurde die Molekülbildung von CaF analysiert, welches für die indirekte, analytische Bestimmung von Fluor in HR-CS-GFMAS genutzt wird. Die CaF Bildung wurde mittels einer Beschichtung aus Zirconium katalysiert und deren Struktur analysiert. Die Kinetik dieser Reaktion wurde durch Beobachtung des jeweiligen Molekülspektrums bei verschiedenen Atomisierungstemperaturen beobachtet. Ein Arrheniusplot zeigte für Fluor (n = 1) eine Reaktion Pseudo-erster Ordnung. Ein Übergangszustand wurde über die mit Zirconium überzogene Grafitoberfläche isoliert und seine Struktur mittels spektroskopischer Methoden Energiedispersive Rasterelektronenmikroskopie / Röntgenspektroskopie (REM-EDX), Röntgenphoto¬elektronenspektroskopie (XPS), Röntgenabsorptionsspektroskopie (XAS) und Raman Spektroskopie untersucht. Auf Grundlage dieser Ergebnisse wird ein Mechanismus vorgeschlagen, bei dem ZrO2 als heterogener Katalysator fungiert; in Folge einer Pyrolysestufe wird ein Übergangszustand des ZrO(OCaF) aktiviert, welcher bei höheren Temperaturen CaF(g) an der Zirconium-Graphitoberfläche freisetzt.
Im zweiten Teil der Arbeit werden Analysemethoden entwickelt, in dem HR-CS-MAS als Detektor für Nichtmetalle und Isotopanalyse angewandt wird. Hierfür wurde organisch gebundenes Chlor im Wasser bestimmt, der Fluorgehalt in Pflegeprodukten mit perfluorierten Inhaltsstoffen quantifiziert und der Schwefelgehalt in Erdöl untersucht. Weiterhin ermöglicht die hohe Auflösung der Messgeräte eine präzise Bestimmung der Isotopenverschiebung einiger untersuchter Molekülspektren. Daher wurden die Molekülspektren angereicherter Bor- und Magnesiumisotope untersucht. Auf diese Weise wurde das Potential von HR-CS-MAS für die akkurate und präzise Bestimmung von Isotop-Mengenverhältnissen nachgewiesen.
Magnesium is a major element in the hydrosphere and biosphere, and it is direct correlated with the carbon cycle. Therefore, the study of its isotopic fractionation in sediments and sea water helps to understand the earth’s climate and global warming. Mg has three stable isotopes, 24Mg, 25Mg and 26Mg, and traditionally isotope amount ratios are measured by mass spectrometric methods. Their drawbacks include the high costs for instruments and their operation, experienced operators and elaborate time-consuming chromatographic sample preparation. Recently, an optical spectrometric method has been proposed as faster and low-cost alternative for the analysis of isotope ratios: high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS-GFMAS).
For the determination of Mg isotope ratios in selected rock reference materials, the high-resolution molecular absorption spectrum of in-situ generated MgF molecule was studied applying multivariate analysis and the results compared with MC-ICP-MS. Samples were dissolved by acid digestion and Mg isotopes analyzed with and without matrix extraction. The absorption spectra were recorded for MgF for the electronic transition X 2Σ → B 2Σ+. The MgF spectrum is described as the linear combination of their isotopic components or isotopologues: 24MgF, 25MgF, and 26MgF. The isotope analysis was done by deconvolution of the MgF spectrum by partial least square regression (PLS). A PLS model was built and calibrated with enriched isotope spikes and certified reference materials. Spectra data was preprocessed by a derivate of second order and venetian blinds cross-validation was employed for finding the optimum latent variables. Finally, the model was refined by a genetic algorithm which identified the best subset of variables for a precise and accurate regression. Results are compatible with those obtained by MC-ICP-MS with an accuracy of ± 0.3‰ with uncertainties ranging between 0.02 to 0.6‰. This accuracy and precision discriminate the isotope fractionation in geological samples, and it is suitable for earth’s climate studies.
Small variations in the isotopic composition of some elements have been used as proof of provenance of mineral and biological samples, to describe geological processes, and to estimate a contamination source. Routinely, isotope compositions are measured by mass spectrometry; the working horse of the isotope analysis. However, mass spectrometric methods are expensive, time-consuming and they require a high qualified analyst.
Here, an alternative faster and low-cost optical method for isotope ratio determination is investigated: high-resolution continuum source molecular absorption spectrometry (HR-CS-MAS). Stable isotope amount composition of X = Li, B, Mg, Ca and Sr have been determined by monitoring the absorption spectra of their in situ generated hydrides (XH) in graphite furnace HR-CS-MAS. For example, the system of two stable isotopes of boron (10B and 11B) was studied via its hydride for the electronic transition X1Σ+ → A1Π (Fig. 1a). The spectrum of a given sample is a linear combination of the 10BH molecule and its isotopologue 11BH. Therefore, isotopic composition of samples and reference materials are calculated by a partial least square regression (PLS). For this, a spectral library is built by using samples with known isotope composition. Results are metrologically compatible with those reported by mass spectrometric methods. [1] Similar results are obtained for n isotope systems like Mg (24Mg, 25Mg, and 26Mg), where isotope shift of their isotopologues can be resolved as shown in Fig.1 b. The extension of this methodology to other elements like Li, Ca and Sr is discussed [2].
References:
[1] C. Abad, S. Florek, H. Becker-Ross, M.-D. Huang, H.-J. Heinrich, S. Recknagel, J. Vogl, N. Jakubowski, U. Panne, Determination of boron isotope ratios by high-resolution continuum source molecular absorption spectrometry using graphite furnace vaporizers, Spectrochim. Acta, Part B, 136 (2017) 116-122.
[2] C. Abad et al., unpublished results, 2018.
An alternative method for lithium isotope analysis by using high-resolution atomic absorption spectrometry (HR-CS-AAS) is proposed herein. This method is based on monitoring the isotope shift of approximately 15 pm for the electronic transition 22P←22S at around the wavelength of 670.8 nm, which can be measured by state-of-the-art HR-CS-AAS. Isotope analysis can be used for (i) the traceable determination of Li concentration and (ii) isotope amount ratio analysis based on a combination of HR-CS-AAS and spectral data analysis by machine learning (ML).
In the first case, the Li spectra are described as the linear superposition of the contributions of the respective isotopes, each consisting of a spin-orbit doublet, which can be expressed as Gaussian components with constant spectral position and width and different relative intensity, reflecting the isotope ratio in the sample. Precision was further improved by using lanthanum as internal spectral standard. The procedure has been validated using human serum-certified reference materials. The results are metrologically comparable and compatible with the certified values.
In the second case, for isotope amount ratio analysis, a scalable tree boosting ML algorithm (XGBoost) was employed and calibrated using a set of samples with 6Li isotope amount fractions ranging from 0.06 to 0.99 mol mol−1. The training ML model was validated with certified reference materials. The procedure was applied to the isotope amount ratio determination of a set of stock chemicals and a BAM candidate reference material NMC111 (LiNi1/3Mn1/3Co1/3O2), a Li-battery cathode material. These determinations were compared with those obtained by MC-ICP-MS and found to be metrologically comparable and compatible. The residual bias was −1.8‰, and the precision obtained ranged from 1.9‰ to 6.2‰. This precision was sufficient to resolve naturally occurring variations. The NMC111 cathode candidate reference material was analyzed using high-resolution continuum source atomic absorption spectrometry with and without matrix purification to assess its suitability for technical applications. The results obtained were metrologically compatible with each other.
Mass spectrometric methods (MC-ICP-MS and TIMS) are without doubt the working horse of stable isotope analysis. However, drawbacks of these methods include the high costs for instruments and their operation, experienced operators and elaborate chromatographic sample preparation which are time consuming.
We propose a lower-cost and faster optical alternative for the analysis of isotope ratios of selected elements: high-resolution continuum source molecular absorption spectrometry (HR-CS-MAS). Stable isotope amount compositions of boron (B) and magnesium (Mg) were determined based on the absorption spectra of in-situ generated mono-hydrides and halide (MH and MX) using graphite furnace HR-CS-MAS. The use of a modular simultaneous echelle spectrograph (MOSES) helps to find the maximal isotope shift in the diatomic molecular spectra produced in a graphite furnace by using isotopic spike solutions. Isotopes of boron (10B and 11B) were studied via their hydrides for the electronic transition X 1Σ+ → A 1Π. The spectrum of a given sample is a linear combination of the 10BH molecule and its isotopologue 11BH. Therefore, the isotopic composition of samples can be calculated by a partial least square regression (PLS). For this, a spectral library was built by using samples and spikes with known isotope composition. Boron isotope ratios measured by HR-CS-MAS are identical with those measured by mass spectrometric methods at the 0.15 ‰ level. Similar results were obtained for a multiple isotope system like Mg (24Mg, 25Mg, and 26Mg), where isotope shifts of their isotopologues can be resolved in the MgF molecule for the electronic transition X 2Σ → A 2 Πi. The extension of this methodology to other elements like Li, Ca, Cu, and Sr is discussed.
Magnesium (Mg) is a major element in a range of silicate and carbonate minerals, the hydrosphere and biosphere and plays important roles in (bio-) geochemical and physiological cycles. Mg has three stable isotopes, 24Mg, 25Mg and 26Mg with natural abundances of 79 %, 10 %, and 11 %, respectively. It is due to their relatively large mass difference (~8% between 24Mg and 26Mg) that isotope fractionation leads to slight variations of isotope amount ratios n(26Mg)/n(24Mg) in biological, environmental and geological samples. Traditionally, isotope ratios are measured by mass spectrometric methods and isotope ratios are expressed as deviation from an internationally agreed upon material, i.e. the zero-point of the δ-value scale. Drawbacks of this method include the high costs for instruments and their operation, experienced operators and elaborate, time-consuming chromatographic sample preparation.
Recently, optical spectrometric methods have been proposed as faster and low-cost alternative for the analysis of isotope ratios of selected elements by means of high- resolution continuum source graphite furnace molecular absorption spectrometry (HR- CS-GFMAS) and laser ablation molecular isotopic spectrometry (LAMIS).
For the determination of Mg isotope amount ratios, the molecular spectrum of the in-situ generated MgF and MgO molecules were studied. In the case of HR-CS-GFMAS, the absorption spectrum was recorded for MgF for the electronic transitions X2Σ → A2Πi and X 2Σ → B2Σ+ around wavelengths 358 nm and 268 nm, respectively. In the case of LAMIS, we investigated the MgF molecule for the electronic transition A2Πi → X2Σ as well as the MgO molecule for the electronic transition A1Π+ → X1Σ around 500 nm. The MgF and MgO spectra are described by the linear combination of their isotopic components or isotopologues: 24MgF, 25MgF, and 26MgF for the MgF and 24MgO, 25MgO, and 26MgO for the MgO (F is monoisotopic, and the isotope composition of O is assumed as constant). By HR-CS-GFMAS the analysis of Mg was done by deconvolution of the MgF spectrum by partial least square regression (PLS) calibrated with enriched isotope spikes. Isotope amount ratios in rock samples with and without matrix separation were analyzed. Calculated δ-values were accurate and obtained with precisions ranging between 0.2 ‰ and 0.5 ‰ (1 SD, n = 10). On the other hand, LAMIS allows the direct analysis of solid samples with the extended possibility of in-situ analysis. Main advantages, limitations, and scopes of both optical techniques are going to be discussed and compared to MC-ICP-MS.
The mechanism of action of zirconium permanent modifiers on graphite surfaces was investigated in order to understand its influence on the analytical signal in atomic and molecular absorption spectrometry (AAS/MAS). For this, the molecule formation of CaF was studied, which is used for the indirect analytical determination of fluorine in high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS-GFMAS). The kinetics of this reaction was established by monitoring its molecular spectrum at different atomisation temperatures. An Arrhenius plot showed a pseudo-first order reaction with respect to fluorine (n = 1). An intermediate state was isolated, and its structure was elucidated by spectroscopic methods: scanning electron microscopy with energy dispersive X-ray spectroscopy (SEMEDX), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XANES and EXAFS), and Raman microspectroscopy. We propose here a mechanism, where ZrO2 acts as a heterogeneous catalyst: after a pyrolytic step, an intermediate state of ZrO(OCaF) is activated, and at higher temperatures, CaF(g) is released from the zirconium-coated graphite surface. No evidence of the formation of zirconium carbide was found. Consequently, as the CaF formation is catalysed by a heterogeneous catalyst, surface modifications with ZrO2 nanoparticles and ZrO xerogels were investigated in order to increase the surface area. Their influence was evaluated in the molecule formation of CaF, CaCl, CaBr, and CaI. Graphite furnace modification with zirconium oxide nanoparticles proves to be the best choice for fluorine analysis with a signal enhancement of more than eleven times with respect a non-coated graphite furnace. However, the influence of zirconium modifications in the analytical signals of Cl, and I is lower than the F signals or even negative in case of the Br. Understanding zirconium modifiers as heterogeneous catalysts offers a new perspective to AAS and MAS, and reveals the potential of surface analytical methods for development of improved permanent modifiers and graphite furnace coatings.
A fast and simple method for sulfur quantification in crude oils was developed by using high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS-GFMAS). For this, heavy crude oil samples were prepared as microemulsion (shake) and injected into a graphite furnace (shut). Finally, the concentration of sulfur was determined by monitoring in situ the transient molecular spectrum of GeS at wavelength 295.205nm after adding a germanium solution as molecular forming agent (and go). Zirconium dioxide in the form of nanoparticles (45–55nm) was employed as a permanent modifier of the graphite furnace. Calibration was done with an aqueous solution standard of ammonium sulfate, and a characteristic mass (m0) of 7.5ng was achieved. The effectiveness of the proposed method was evaluated analizing, ten heavy crude oil samples with Sulfur amounts ranging between 0.3 and 4.5% as well as two NIST standard reference materials, 1620c and 1622e. Results were compared with those obtained by routine ICP-OES analysis, and no statistical relevant differences were found.
High-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS-GF-MAS) was employed for determining adsorbable organic chlorine (AOCl) in water. Organic chlorine was indirectly quantified by monitoring the molecular absorption of the transient aluminum monochloride molecule (AlCl) around a wavelength of 261.42 nm in a graphite furnace. An aluminum solution was used as the molecularforming modifier. A zirconium coated graphite furnace, as well as Sr and Ag solutions were applied as modifiers for a maximal enhancement of the absorption signal. The pyrolysis and vaporization temperatures were 600 °C and 2300 °C, respectively. Non-spectral interferences were observed with F, Br, and I at concentrations higher than 6 mg L-1, 50 mg L-1, and 100 mg L-1, respectively. Calibration curves with NaCl, 4-chlorophenol, and trichlorophenol present the same slope and dynamic range, which indicates the chlorine atom specificity of the method. This method was evaluated and validated using synthetic water samples, following the current standard DIN EN ISO 9562:2004 for the determination of the sum parameter adsorbable organic halides (AOX) for water quality. These samples contain 4-chlorophenol as the chlorinated organic standard in an inorganic chloride matrix. Prior to analysis, organic chlorine was extracted from the inorganic matrix via solid-phase extraction with a recovery rate >95%. There were no statistically significant differences observed between measured and known values and for a t-test a confidence level of 95% was achieved. The limits of detection and characteristic mass were found to be 48 and 22 pg, respectively. The calibration curve was linear in the range 0.1–2.5 ng with a correlation coefficient R2 = 0.9986.
Isotope-dilution liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) is emerging in the field of clinical chemistry and laboratory medicine as an alternative to immunoassays and is acknowledged as the MS “gold standard” for small biomolecule quantification. Hepcidin-25, a key iron-regulatory peptide hormone discovered in 2000, has revolutionized the understanding of iron disorders and its quantitative determination in biological samples should advance the management of iron-related pathology (diagnosis, prognosis and treatment). This study applied LC-MS/MS, using the triple quadrupole (QqQ) mass spectrometer, in a rapid and robust analytical strategy for the quantification of hepcidin-25 in human serum, to be implemented in routine laboratories. For this purpose, two sample preparation strategies and two complementary chromatographic separation conditions were investigated, where the use of acidic mobile phases (0.1% trifluoroacetic acid) was compared with a novel approach involving solvents at high pH (containing 0.1% ammonia). The application of these LC-MS/MS methods to human samples in an intra-laboratory comparison, using the same hepcidin-25 calibrators, yielded a very good correlation of the results. The LC-MS/MS employing trifluoroacetic acid-based mobile phases was selected as a highly sensitive (limit of quantification LOQ of 0.5 μg/L) and precise (coefficient of variation CV<15%) method and was recommended as a reference method candidate for hepcidin-25 quantification in real samples (in the dynamic range of 0.5-40 μg/L). One of the novel aspects of the methodology was the use of amino- and fluoro-silanized autosampler vials to reduce the interaction of the 25-residue peptide to laboratory glassware surfaces. Moreover, this LC-MS/MS method was used for an international round robin study, applying a secondary reference material as a calibrator. By determining the degree of equivalence between the results of the ten participating methodologies, the performance of the method developed in this study was found to be in the optimal range as defined by the International Consortium for Harmonization of Clinical Laboratory Results (ICHCLR). In this work, the formation of hepcidin-25 complexes with copper(II) was investigated. The first reversed-phase chromatographic separation of hepcidin-25/Cu2+ and hepcidin-25 (copper “free”) was achieved by applying mobile phases containing 0.1% of ammonia (pH 11). LC-MS/MS and high-resolution mass spectrometry (Fourier-transform ion cyclotron resonance (FTICR) MS) were applied for the mass spectrometric characterization of the formed hepcidin-25-Cu(II) species at pH values of 11 and 7.4 respectively. A new species corresponding to hepcidin-25 complexed with two copper ions was identified at high pH.
Hepcidin-25 has attracted much attention ever since its discovery in 2001. It is widely recognized that this peptide hormone plays a major role in the regulation of iron levels in mammals and can reveal important clinical information about several iron-related disorders. However, the development of a reliable assay to quantify hepcidin proved to be problematic and serum hepcidin-25 concentrations determined by various assays differ substantially. Challenges arise in the MS analysis of hepcidin due to the “sticky” character of the peptide and the lack of suitable standards.
With the aim to tackle the current difficulties in hepcidin quantification and improve the status of this promising biomarker in the clinical field, we developed a rapid and robust analytical strategy for the quantification of hepcidin-25 in human samples based on HPLC-MS/MS (QqQ) as a reference method candidate to be implemented in routine laboratories. The novelty of the method is the use of amino- and fluoro-silanized autosampler vials to reduce hepcidin interaction to laboratory glassware surfaces. Furthermore, we have investigated two sample preparation strategies and two chromatographic separation conditions where the use of acidic mobile phases was compared with a novel approach involving solvents at high pH containing 0.1% of ammonia. Both methods were carefully validated and applied to clinical samples in an intra-laboratory comparison of two LC-MS/MS methods using the same hepcidin-25 calibrators with very good correlation of the results.
Mass spectrometry-based methods play a crucial role in the quantification of the main iron metabolism regulator hepcidin by singling out the bioactive 25-residue peptide from the other naturally occurring N-truncated isoforms (hepcidin-20, -22, -24), which seem to be inactive in iron homeostasis. However, several difficulties arise in the MS analysis of hepcidin due to the sticky character of the peptide and the lack of suitable standards. Here, we propose the use of amino- and fluoro-silanized autosampler vials to reduce hepcidin interaction to laboratory glassware surfaces after testing several types of vials for the preparation of stock solutions and serum samples for isotope dilution liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS). Furthermore, we have investigated two sample preparation strategies and two chromatographic separation conditions with the aim of developing an LC-MS/MS method for the sensitive and reliable quantification of hepcidin-25 in serum samples. A chromatographic separation based on usual acidic mobile phases was compared with a novel approach involving the separation of hepcidin-25 with solvents at high pH containing 0.1% of ammonia. Both methods were applied to clinical samples in an intra-laboratory comparison of two LC-MS/MS methods using the same hepcidin-25 calibrators with good correlation of the results. Finally, we recommend an LC-MS/MS-based quantification method with a dynamic range of 0.5–40 μg/L for the assessment of hepcidin-25 in human serum that uses TFA-based mobile phases and silanized glass vials.
Hepcidin-25 was identified as the main iron regulator in the human body, and it by binds to the sole iron-exporter ferroportin. Studies showed that the N-terminus of hepcidin is responsible for this interaction, the same N-terminus that encompasses a small copper(II)-binding site known as the ATCUN (amino-terminal Cu(II)- and Ni(II)-binding) motif. Interestingly, this copper-binding property is largely ignored in most papers dealing with hepcidin-25. In this context, detailed investigations of the complex formed between hepcidin-25 and copper could reveal insight into its biological role. The present work focuses on metal-bound hepcidin-25 that can be considered the biologically active form. The first part is devoted to the reversed-phase chromatographic separation of copper-bound and copper-free hepcidin-25 achieved by applying basic mobile phases containing 0.1% ammonia. Further, mass spectrometry (tandem mass spectrometry (MS/MS), high-resolution mass spectrometry HRMS)) and nuclear magnetic resonance (NMR) spectroscopy were employed to characterize the copper-peptide. Lastly, a three-dimensional (3D)model of hepcidin-25with bound copper(II) is presented. The identification of metal complexes and potential isoforms and isomers, from which the latter usually are left undetected by mass spectrometry, led to the conclusion that complementary analytical methods are needed to characterize a peptide calibrant or reference material comprehensively. Quantitative nuclear magnetic resonance (qNMR), inductively-coupled plasma mass spectrometry (ICP-MS), ion-mobility spectrometry (IMS) and chiral amino acid analysis (AAA) should be considered among others.
Microfluidic electrochemical immunosensor for the trace analysis of cocaine in water and body fluids
(2018)
Quick but accurate testing and on‐the‐spot monitoring of cocaine in oral fluids and urine continues to be an important toxicological issue. In terms of drug testing, a number of devices have been introduced into the market in recent decades, notably for workplace inspection or roadside testing. However, these systems do not always fulfill the requirements in terms of reliability, especially when low cut‐off levels are required. With respect to surface water, the presence of anthropogenic small organic molecules such as prescription and over‐the‐counter pharmaceuticals as well as illicit drugs like cannabinoids, heroin, or cocaine, has become a challenge for scientists to develop new analytical tools for screening and on‐site analysis because many of them serve as markers for anthropogenic input and consumer behavior. Here, a modular approach for the detection of cocaine is presented, integrating an electrochemical enzyme‐linked immunosorbent assay (ELISA) performed on antibody‐grafted magnetic beads in a hybrid microfluidic sensor utilizing flexible tubing, static chip and screen‐printed electrode (SPE) elements for incubation, recognition, and cyclic voltammetry measurements. A linear response of the sensor vs. the logarithm of cocaine concentration was obtained with a limit of detection of 0.15 ng/L. Within an overall assay time of 25 minutes, concentrations down to 1 ng/L could be reliably determined in water, oral fluids, and urine, the system possessing a dynamic working range up to 1 mg/L.
Microfluidic electrochemical immunosensor for the trace analysis of cocaine in water and body fluids
(2018)
Quick but accurate testing and on‐the‐spot monitoring of cocaine in oral fluids and urine continues to be an important toxicological issue. In terms of drug testing, a number of devices have been introduced into the market in recent decades, notably for workplace inspection or roadside testing. However, these systems do not always fulfill the requirements in terms of reliability, especially when low cut‐off levels are required. With respect to surface water, the presence of anthropogenic small organic molecules such as prescription and over‐the‐counter pharmaceuticals as well as illicit drugs like cannabinoids, heroin, or cocaine, has become a challenge for scientists to develop new analytical tools for screening and on‐site analysis because many of them serve as markers for anthropogenic input and consumer behavior. Here, a modular approach for the detection of cocaine is presented, integrating an electrochemical enzyme‐linked immunosorbent assay (ELISA) performed on antibody‐grafted magnetic beads in a hybrid microfluidic sensor utilizing flexible tubing, static chip and screen‐printed electrode (SPE) elements for incubation, recognition, and cyclic voltammetry measurements. A linear response of the sensor vs. the logarithm of cocaine concentration was obtained with a limit of detection of 0.15 ng/L. Within an overall assay time of 25 minutes, concentrations down to 1 ng/L could be reliably determined in water, oral fluids, and urine, the system possessing a dynamic working range up to 1 mg/L.
One of the major challenges in chemical synthesis is to trigger and control a specific reaction route leading to a specific final product, while side products are avoided. Methodologies based on resonant processes at the molecular level, for example, photochemistry, offer the possibility of inducing selective reactions. Electrons at energies below the molecular ionization potential (<10 eV) are known to dissociate molecules via resonant processes with higher cross sections and specificity than photons. Here we show that even subexcitation electrons with energies as low as 1 eV produce ethylene and acetylene from dimethyl sulfide in competing reactions. However, the production of ethylene can specifically be targeted by controlling the energy of electrons (∼3 to 4 eV). Finally, pure ethylene is selectively desorbed by heating the substrate from 90 to 105 K. Beyond the synthesis of these versatile hydrocarbons for various industrial applications from a biogenic sulfur compound, our findings demonstrate the feasibility of electron-induced selective chemistry applicable on the nanoscale.
Trialkoxysilane haben sich in den vergangenen Jahren als vielseitig einsetzbare Organosilane erwiesen. Die Einsatzgebiete erstrecken sich vom Witterungsschutz von Bauwerken über haftvermittelnde Eigenschaften in der Glasfaserindustrie, bei Dicht- und Klebstoffen, in Farben und Lacken bis hin zur Modifizierung von polymeren Werkstoffen.
Kommerzielle Benchtop-NMR-Spektrometer haben das Potential auch im Bereich der Silanchemie als Online-Methode zur Reaktionsüberwachung und für die Qualitätskontrolle eingesetzt zu werden. Interessante NMR-Kerne für die oben genanntem Produkte sind 1H und 29Si. In einer gemeinsamen Forschungskooperation zwischen EVONIK und BAM wurde anhand verschiedener Fallstudien die Anwendbarkeit der Niederfeld-NMR-Spektroskopie zur chemischen Analyse von Silanen evaluiert. Im Zuge der Fallstudien wurde gezeigt, wie Niederfeld-NMR-Spektroskopie die Möglichkeiten der Konzentrationsmessung auf neue Anwendungsgebiete erweitert, in denen bestehende Technologien wie z. B. NIR, Raman, UV/VIS, etc. mangels Referenzdaten nicht quantitativ eingesetzt werden können.
Fallstudie 1: Oligomerisierung
Eine Fallstudie setzte dazu an, den Hydrolyse- und Kondensationsverlauf mit einer geeigneten Online-NMR-Analytik zu beobachten, den Reaktionsfortschritt der Hydrolyse und Kondensation auf dieser Basis besser zu verstehen und zu optimieren. Zu diesem Zweck werden durch Zugabe von Wasser zunächst die Alkoxysubstituenten eines Trialkoxysilans hydrolysiert und entsprechende Silanole gebildet. Diese können dann über eine SiOH-Funktion an den zu modifizierenden Werkstoff anbinden und über weitere Silanolgruppen unter Ausbildung von Siloxaneinheiten vernetzen.
Fallstudie 2: Spaltung von cyclischen Silanverbindungen
In einer weiteren Fallstudie wurde die Kinetik der Aufspaltungen einer cyclischen Silanverbindung untersucht. Die Online-NMR-Analytik kam hierbei sowohl im Labor als auch in der industriellen Produktionsanlage zum Einsatz. Hierfür wurde eine vollständig automatisierte Einhausung verwendet, welche den Einsatz eines kommerziellen NMR-Spektrometers in explosionsgeschützten Bereichen ermöglicht.
Fallstudie 3: Qualitätskontrolle für Produktmischungen von Trialkoxysilanen
Für Produktmischungen eines Trialkoxysilans und weiteren Bestandteilen wie u. a. org. Stabilisatoren, Organozinnverbindungen, eines aromatischen Amins und org. Peroxide wurden quantitative 1H-Spektren akquiriert und eine automatische Auswertungsmethode basierend auf Indirect Hard Modeling (IHM) entwickelt. Für die Nebenkomponenten, deren Stoffmengenanteile bis zu 3 Mol-% betragen, wurden durch die zugrunde gelegte Methode typischerweise korrekte experimentelle Stoffmengenanteile gefunden, die weniger als 0,2 Mol-% vom Referenzwert abweichen.
Monodisperse iron oxide nanoparticles as reference material candidate for particle size measurements
(2020)
In order to utilize and rationally design materials at the nanoscale the reliable characterization of their physico-chemical properties is highly important, especially with respect to the assessment of their environmental or biological impact. Furthermore, the European Commission’s REACH Regulations require the registration of nanomaterials traded in quantities of at least 1 ton. Powders or dispersions where 50% (number distribution) of the constituent particles have sizes ≤ 100 nm in at least one dimension are defined as nanomaterials. This creates a need for industrial manufacturers and research or analytical service facilities to reliably characterize potential nanomaterials. Currently, BAM is developing reference nanoparticles, which shall expand the scarce list of worldwide available nano reference materials certified for particle size distribution and will also target other key parameters like shape, structure, porosity or functional properties. In this respect, materials like iron oxide or titanium dioxide are considered as candidates to complement the already available silica, Au, Ag, and polystyrene reference nanoparticles.
The thermal decomposition of iron oleate precursors in high boiling organic solvents can provide large quantities of iron oxide nanoparticles that can be varied in size and shape.[1, 2] The presence of oleic acid or other hydrophobic ligands as capping agents ensures stable dispersion in nonpolar solvents. Such monodisperse, spherical particles were synthesized at BAM and pre-characterized by electron microscopy (TEM, SEM including the transmission mode STEM-in-SEM) and dynamic light scattering comparing cumulants analysis and frequency power spectrum.
1. REACH regulations and nanosafety concerns create a strong need for nano reference materials with diverse properties.
2. Iron oxide nanoparticles are under development as new candidate reference material at BAM.
3. Narrow particle size distribution confirmed by light scattering and electron microscopy.
Iron Oxide Nanocubes as a New Certified Reference Material for Nanoparticle Size Measurements
(2023)
The rational design and increasing industrial use of nanomaterials require a reliable characterization of their physicochemical key properties like size, size distribution, shape, and surface chemistry. This calls for nanoscale reference materials (nanoRMs) for the validation and standardization of commonly used characterization methods closely matching real-world nonspherical nano-objects. This encouraged us to develop a nonspherical nanoRM of very small size consisting of 8 nm iron oxide nanocubes (BAM-N012) to complement spherical gold, silica, and polymer nanoRMs. In the following, the development and production of this nanoRM are highlighted including the characterization by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) as complementary methods for size and shape parameters, homogeneity and stability studies, and calculation of a complete uncertainty budget of the size features. The determination of the nanocubes’ edge length by TEM and SAXS allows a method comparison. In addition, SAXS measurements can also provide the mean particle number density and the mass concentration. The certified size parameters, area equivalent circular diameter and square edge length, determined by TEM with a relative expanded uncertainty below 9%, are metrologically traceable to a natural constant for length, the very precisely known (111) lattice spacing of silicon. Cubic BAM-N012 qualifies as a certified nanoRM for estimating the precision and trueness, validation, and quality assurance of particle size and shape measurements with electron microscopy and SAXS as well as other sizing methods suitable for nanomaterials. The production of this new iron oxide nanocube RM presents an important achievement for the nanomaterial community, nanomaterial manufacturers, and regulators.
The project “Intelligence for Soil” (I4S) aims at the design of an integrated system for improvement of soil functions and fertilizer recommendations. This system is composed by different sensors that will provide a detailed assessment of soil properties and processes, which are prerequisites for a site-specific, resource-saving and ecofriendly soil management, considering the soil as a sustainable resource for the bioeconomy. One of these sensors will be an energy-dispersive X-Ray Fluorescence spectrometer. It is a non-destructive technique suitable for in-situ measurements due to a minimum sample preparation and it allows fast multielement analyses. In this work, an automatic system has been developed using a handheld equipment from Olympus (Vanta C series). A polypropylene (PP) film was used to protect the measuring window of the device from dust and possible cross-contamination. To control the stepper motor that unrolls the PP film, a microcontroller was used to ensure that a piece of clean PP is in front of the measuring window for each new analysis.
Preliminary calibration studies using pre-defined methods, Geochem and Soil Methods, were performed with the following Certified Reference Materials (CRMs): NRC Till 1-3, NIST 2710, BAM U110, ERM CC141, BCR 142R, IAEA Soil 7. The CRMs were measured 10 times at different spots. The spot size was 10 mm in diameter, irradiation time was 60 ? s. The averaged data from X ray characteristic emission line intensities for Al, P, Si, Ca, Fe, Mn, Zn, Cu and Ni Kα were in close agreement with certified mass fraction data. The linear correlation coefficients (r) ranged from 0.852 for P to 0.999 for Mn. A second round of calibration studies were performed with the following CRMs: GBW07402, GBW 07405, NCS DC 73023, NCS DC 73030, NCS DC 85109, NCS DC 87104, NIST 1646a, NIST 2704, NIST 2710, NRC Till 1-3, VS 2498-83, and the same pre-defined methods and experimental parameters were employed. The results of the 13 CRMs were now compared with the values obtained by a validated WDXRF method. The linear correlation coefficients (r) ranged from 0.998 for Ca to 0.999 for Zn. Other elements such as S, K and Ti can also be properly determined, but validation still requires more robust calibration models.
Further calibration studies will be performed in order to circumvent matrix effects and to guarantee reliable results. Besides that, the automatic system will be placed on a mobile sensor platform and the system will be tested in the field. A guidance for on site-specific fertilization integrating the results obtained from different sensors placed on the platform is expected.
Background. Currently, there is no reliable nonsurgical treatment for abdominal aortic aneurysm (AAA). This study, therefore, investigates if doxycycline reduces AAA growth and the number of rupture-related deaths in a murine ApoE−/− model of AAA and whether gadofosveset trisodium-based MRI differs between animals with and without doxycycline treatment. Methods. Nine ApoE−/− mice were implanted with osmotic minipumps continuously releasing angiotensin II and treated with doxycycline (30 mg/kg/d) in parallel. After four weeks, MRI was performed at 3T with a clinical dose of the albumin-binding probe gadofosveset (0.03 mmol/kg). Results were compared with previously published wild-type control animals and with previously studied ApoE−/− animals without doxycycline treatment. Differences in mortality were also investigated between these groups. Results. In a previous study, we found that approximately 25% of angiotensin II-infused ApoE−/− mice died, whereas in the present study, only one out of 9 angiotensin II-infused and doxycycline-treated ApoE−/− mice (11.1%) died within 4 weeks. Furthermore, doxycycline-treated ApoE−/− mice showed significantly lower contrast-to-noise (CNR) values in MRI compared to ApoE−/− mice without doxycycline treatment. In vivo measurements of relative signal enhancement (CNR) correlated significantly with ex vivo measurements of albumin staining (R2 = 0.58). In addition, a strong visual colocalization of albumin-positive areas in the fluorescence albumin staining with gadolinium distribution in LA-ICP-MS was shown. However, no significant difference in aneurysm size was observed after doxycycline treatment. Conclusion. The present experimental in vivo study suggests that doxycycline treatment may reduce rupture-related deaths in AAA by slowing endothelial damage without reversing aneurysm growth.
Abdominal aortic aneurysm (AAA) is a life-threatening vascular disease with an up to 80% mortality in case of rupture. Current biomarkers fail to account for size-independent risk of rupture. By combining the information of different molecular probes, multi-target molecular MRI holds the potential to enable individual characterization of AAA. In this experimental study, we aimed to examine the feasibility of simultaneous imaging of extracellular collagen and inflammation for size-independent prediction of risk of rupture in murine AAA. The study design consisted of: (1) A outcome-based longitudinal study with imaging performed once after one week with follow-up and death as the end-point for assessment of rupture risk. (2) A week-by-week study for the characterization of AAA development with imaging after 1, 2, 3 and 4 weeks. For both studies, the animals were administered a type 1 collagen-targeted gadolinium-based probe (surrogate marker for extracellular matrix (ECM) remodeling) and an iron oxide-based probe (surrogate marker for inflammatory activity), in one imaging session. In vivo measurements of collagen and iron oxide probes showed a significant correlation with ex vivo histology (p < 0.001) and also corresponded well to inductively-coupled plasma-mass spectrometry and laser-ablation inductively-coupled plasma mass spectrometry. Combined evaluation of collagen-related ECM remodeling and inflammatory activity was the most accurate predictor for AAA rupture (sensitivity 80%, specificity 100%, area under the curve 0.85), being superior to information from the individual probes alone. Our study supports the feasibility of a simultaneous assessment of collagen-related extracellular matrix remodeling and inflammatory activity in a murine model of AAA.
Abdominal aortic aneurysm (AAA) remains a fatal disease. Its development encompasses a complex interplay between hemodynamic stimuli on and changes in the arterial wall. Currently available biomarkers fail to predict the risk of AAA rupture independent of aneurysm size. Therefore, novel biomarkers for AAA characterization are needed. In this study, we used a mouse model of AAA to investigate the potential of magnetic resonance imaging (MRI) with an albumin-binding probe to assess changes in vascular permeability at different stages of aneurysm growth. Two imaging studies were performed: a longitudinal study with follow-up and death as endpoint to predict rupture risk and a week-by-week study to characterize AAA development. AAAs, which eventually ruptured, demonstrated a significantly higher in vivo MR signal enhancement from the albumin-binding probe (p = 0.047) and a smaller non-enhancing thrombus area compared to intact AAAs (p = 0.001). The ratio of albumin-binding-probe enhancement of the aneurysm wall to size of non-enhancing-thrombus-area predicted AAA rupture with high sensitivity/specificity (100%/86%). More advanced aneurysms with higher vascular permeability demonstrated an increased uptake of the albumin-binding-probe. These results indicate that MRI with an albumin-binding probe may enable noninvasive assessment of vascular permeability in murine AAAs and prediction of rupture risk.
Background: Prevention of metastatic invasion is one of the main challenges in the treatment of alveolar rhabdomyosarcoma. Still the therapeutic options are limited. Therefore, an anti-tumor screening was initiated focusing on the anti-metastatic and anti-invasion properties of selected medicinal plant extracts and phytoestrogens, already known to be effective in the prevention and treatment of different cancer entities.
Methods: Treatment effects were first evaluated by cell viability, migration, invasion, and colony forming assays on the alveolar rhabdomyosarcoma cell line RH-30 in comparison with healthy primary cells.
Results: Initial anti-tumor screenings of all substances analyzed in this study, identified the plant extract of Vincetoxicum arnottianum (VSM) as the most promising candidate, harboring the highest anti-metastatic potential. Those significant anti-motility properties were proven by a reduced ability for migration (60%), invasion (99%) and colony formation (61%) under 48 h exposure to 25 μg/ml VSM. The restricted motility features were due to an induction of the stabilization of the cytoskeleton – actin fibers were 2.5-fold longer and were spanning the entire cell. Decreased proliferation (PCNA, AMT, GCSH) and altered metastasis (e. g. SGPL1, CXCR4, stathmin) marker expression on transcript and protein level confirmed the significant lowered tumorigenicity under VSM treatment. Finally, significant alterations in the cell metabolism were detected for
25 metabolites, with levels of uracil, N-acetyl serine and propanoyl phosphate harboring the greatest alterations. Compared to the conventional therapy with cisplatin, VSM treated cells demonstrated a similar metabolic shutdown of the primary cell metabolism. Primary control cells were not affected by the VSM treatment.
Conclusions: This study revealed the VSM root extract as a potential, new migrastatic drug candidate for the putative treatment of pediatric alveolar rhabdomyosarcoma with actin filament stabilizing properties and accompanied by a marginal effect on the vitality of primary cells.
Ethnopharmacological relevance: Berberis orthobotrys (BORM) is a medical plant with a long history in traditional usage for the treatment of wounds, cancer, gastrointestinal malady and several other diseases. Our previous studies identified the endemic Pakistani plant Berberis orthobotrys Bien. ex Aitch. as promising source for the treatment of breast cancer and osteosarcoma.
Aim of the study: The present study was aimed to evaluate the anti-cancer properties of 26 plant derived extracts and compounds including the methanolic root extract of Berberis orthobotrys (BORM) on pediatric alveolar rhabdomyosarcoma (RMA), which is known to develop drug resistance, metastatic invasion and potential Tumor progression.
Materials and methods: The main anti-tumor activity of BORM was verified by focusing on morphological, cell structural and metabolic alterations via metabolic profiling, cell viability measurements, flow cytometry, western blotting and diverse microscopy-based methods using the human RMA cell line Rh30.
Results: Exposure of 25 μg/ml BORM exerts an influence on the cell stability, the degradation of oncosomes as well as the shutdown of the metabolic activity of RMA cells, primarily by downregulation of the energy metabolism.
Therefore glycyl-aspartic acid and N-acetyl serine decreased moderately, and uracil increased intracellularly. On healthy, non-transformed muscle cells BORM revealed very low metabolic alterations and nearly no cytotoxic impact. Furthermore, BORM is also capable to reduce Rh30 cell migration (~50%) and proliferation (induced G2/M cycle arrest) as well as to initiate apoptosis confirmed by reduced Bcl-2, Bax and PCNA expression and induced PARP-1 cleavage.
Conclusions: The study provides the first evidence, that BORM treatment is effective against RMA cells with low side effects on healthy cells.
Photon upconversion upon 1550 nm excitation is of high relevance for applications in the third biological excitation window, for photovoltaics beyond current limitations, and enables appealing options in the field of glass Fiber telecommunications. Trivalent doped erbium ions (Er3+) are the material of choice for 1550 nm excited upconversion, however, they suffer from a low absorption cross-section and a low brightness. Therefore, the ability of Silicon metasurfaces to provide greatly enhanced electrical near-fields is employed to enable efficient photon upconversion even at low external Illumination conditions. Hexagonally shaped β-NaYF4:Er3+ nanoparticles are placed on large-area silicon metasurfaces designed to convert near-infrared (1550 nm) to visible light. More than 2400-fold enhanced photon upconversion luminescence is achieved by using this metasurface instead of a planar substrate.
With the aid of optical simulations based on the finite-element method, this result is attributed to the coupling of the excitation source with metasurface resonances at appropriate incident angles. Analysis of the excitation power density dependence of upconversion luminescence and red-to-green-emission ratios enables the estimation of nanoscale near-field enhancement on the metasurface. The findings permit the significant reduction of required external excitation intensities for photon upconversion of 1550 nm light, opening perspectives in biophotonics, telecommunication, and photovoltaics.
Enhanced photon upconversion using erbium-doped nanoparticles interacting with silicon metasurfaces
(2021)
Photon upconversion (UC) using trivalent erbium (Er+3) doped crystals is a promising concept to harness near infrared photons of the solar spectrum which cannot be directly absorbed by silicon solar cells. However, their UC efficiency at low-intensity 1 sun illumination is not relevant on device level so far. Exploiting giant near-field enhancement effects on metasurfaces is an appealing approach to enable efficient UC at low irradiance conditions. Here, we report on more than 1000-fold enhanced photon UC of NaYF4:Er+3 nanoparticles interacting with the near-fields supported by a silicon metasurface under 1550 nm excitation.
Eu2+ is used to replace toxic Pb2+ in metal halide perovskite nanocrystals (NCs). The synthesis implies injection of cesium oleate into a solution of europium (II) bromide at an experimentally determined optimum temperature of 130 ○C and a reaction time of 60 s. Structural analysis indicates the formation of spherical CsEuBr3 nanoparticles with a mean size of 43 ± 7 nm. Using EuI2 instead of EuBr2 leads to the formation of 18-nm CsI nanoparticles, while EuCl2 does not show any reaction with cesium oleate forming 80-nm EuCl2 nanoparticles.
The obtained CsEuBr3 NCs exhibit bright blue emission at 413 nm (FWHM 30 nm) with a room temperature photoluminescence quantum yield of 39%. The emission originates from the Laporte-allowed 4f7–4f65d1 transition of Eu2+ and shows a PL decay time of 263 ns.
The long-term stability of the optical properties is observed, making inorganic lead-free CsEuBr3 NCs promising deep blue emitters for optoelectronics.
Living organisms constantly interact with their environment, including through the exchange of gases. Respiration and the release and uptake of volatile organic compounds (VOCs) create dynamic microenvironments in biological systems. Studying the kinetics of volatiles in biological systems requires expensive instruments, and data analysis is challenging. Therefore, we aimed to design a minimal analytical device for measuring the composition of gaseous mixtures in realtime.
We built the ‘Modular Biological Mass Spectrometer’ (MoBiMS) from 3D-printed parts and custom sensors to fit a wide array of experimental set-ups. We tested the chemical detection range and temporal resolution of the MoBiMS employing pure compounds and complex biological samples.
Compounds with a higher than 0.4 mmHg vapor pressure and a molecular weight up to 154 g/mol were reliably sensed within seconds. The generated electron impact (EI) spectra were directly comparable with standard databases like the NIST EI library. Under a direct analysis approach, the MoBiMS identified the characteristic odor of banana (Musa sp.), that is, isoamyl acetate; tracked the dynamics of CO2 release while the Alka-Seltzer® reaction occurred showed the kinetics of the transient production and consumption of carbon dioxide during photosynthesis. MoBiMS also discriminated between volatile compounds ions coming from tobacco (Nicotiana benthamiana) leaves and the surrounding air through untargeted analysis. The small footprint of the MoBiMS and its relatively low energy consumption facilitate in situ analyses, as an additional gas supply is not necessary with EI ionization. The MoBiMS is easy to assemble, and its construction and operation are very cost-efficient compared to commercial devices. The analytical performance of the MoBiMS is suitable for real-time studies of biological systems, environmental monitoring, and medical diagnostics.
Zusätzlich zu Methodenentwicklung, Miniaturisierung und Kopplungsverfahren zeigen sich die Hyperspektroskopie zusammen mit Imaging‐Verfahren, der Einzelmolekülnachweis und der Einsatz von 3‐D‐Druckern als neue Schwerpunkte. Hinzu kommen künstliche Intelligenz bei Sensoren, Bildgebungsverfahren und Prozesssteuerung sowie die Vernetzung von Analyse‐ und Laborgeräten. Trends und Forschungsthemen aus der analytischen Chemie, zusammengestellt von elf Autoren, koordiniert von Günter Gauglitz.
Carbamazepine (CBZ) and cetirizine (CTZ) are pharmaceutical drugs detected in the aquatic environment. However, the effects to marine invertebrates derived from the combination of these drugs with decreased pH conditions due to ocean acidification are poorly explored. This study investigated the biochemical parameters related to metabolic capacity and oxidative stress response and the transcription of genes related to the mode of action (MoA) of CBZ (1.0 μg/L) and CTZ (0.6 μg/L) in the clam Ruditapes philippinarum chronically exposed (28 days) to control (7.8) and low (7.5) pH conditions. The biochemical parameters applied were: the activity of electron transport system (indicator of organisms’ metabolic capacity); lipid peroxidation content (indicator of cell damage); total glutathione peroxidase activity (indicator of antioxidant defense). The transcription of genes related with drug neurotransmission and metabolism, cell defense and immunity and biomineralization was studied. No metabolic changes and oxidative stress was induced by the exposure to CBZ or CTZ at each pH level, but the transcription of several genes related with the MoA (neurotransmission, immunity and biomineralization) was altered by low pH, drug exposure and the combination of both stressors. In conclusion, it was shown that the interaction of drug exposure and low pH conditions can change bivalves’ sensitivity to drugs or alter drugs toxicity.
In coastal systems, organisms are exposed to amultitude of stressors whose interactions and effects are poorly studied. Pharmaceutical drugs and Climate Change consequences, such as lowered pH, are examples of stressors affecting marine organisms, as bivalves. Although a vast literature is available for the effects of these stressors when acting individually, very limited information exists on the impacts that the combination of both can have on marine bivalves. For this reason, this study aimed to evaluate the impacts of a simulated ocean acidification scenario (control pH, 8.0; lowered pH, pH 7.6) on the effects of the antiepileptic carbamazepine (CBZ, 1 μg/L) and the antihistamine cetirizine (CTZ, 0.6 μg/L), when acting individually and combined (CBZ + CTZ), on the edible clam Ruditapes philippinarum. After 28 days of exposure, drug concentrations, bioconcentration factors and biochemical parameters related to the clams' metabolic capacity and oxidative stress were evaluated. The results showed that R. philippinarum clams responded differently to pharmaceutical drugs depending on the pH tested, influencing both bioconcentration and biological responses. In general, drug combined treatments showed fewer impacts than drugs acting alone, and acidification seemed to activate at a higher extension the elimination processes that were not activated under control pH. Also, lowered pH per se exerted negative impacts (e.g., cellular damage) on R. philippinarum and the combination with pharmaceutical drugs did not enhance the toxicity.
The negative effects induced in marine organisms by Climate Change related abiotic factors consequences, namely ocean warming, are well-known. However, few works studied the combined impacts of ocean warming and contaminants, as pharmaceutical drugs. Carbamazepine (CBZ) and cetirizine (CTZ) occur in the marine environment, showing negative effects in marine organisms. This study aimed to evaluate the impacts of Ocean warming on the effects of CBZ and CTZ, when acting individually and combined (drug vs drug), in the edible clam Ruditapes philippinarum. For that, drugs concentration, bioconcentration factors and biochemical parameters, related with clam’s metabolic capacity and oxidative stress, were evaluated after 28 days exposure to environmentally relevant scenarios of these stressors. The results showed limited impacts of the drugs (single and combined) at control and warming condition. Indeed, it appeared that warming improved the oxidative status of contaminated clams (higher reduced to oxidized glutathione ratio, lower lipid peroxidation and Protein carbonylation levels), especially when both drugs were combined. This may result from clam’s defence mechanisms activation and reduced metabolic capacity that, respectively, increased elimination and limited production of reactive oxygen species. At low stress levels, defence mechanisms were not activated which resulted into oxidative stress. The present findings highlighted that under higher stress levels clams may be able to activate defence strategies that were sufficient to avoid cellular damages and loss of redox homeostasis.
Nevertheless, low concentrations were tested in the present study and the observed responses may greatly Change under increased pollution levels or temperatures. Further research on this topic is needed since marine heat waves are increasing in frequency and intensity and pollution levels of some pharmaceuticals are also increasing in coastal systems.
In the aquatic environment, organisms are exposed to complex mixtures of contaminants which may alter the toxicity profile of each compound, compared to its toxicity alone. Pharmaceutical drugs (e.g. carbamazepine (CBZ) and cetirizine (CTZ)) and metals (e.g. cadmium (Cd)) are among those contaminants that co-occur in the environment. However, most studies concerning their toxicity towards aquatic species are based on single exposure experiments. Thus, the present study aimed to evaluate single and combined effects of Cd and CBZ or CTZ (single conditions: Cd, CTZ, CBZ; combined conditions: CTZ+Cd, CBZ+Cd) on biomarkers related to oxidative stress and energy metabolism in the edible clam Ruditapes philippinarum, by exposing the organisms for 28 days to environmentally relevant concentrations of these contaminants. The biomarkers studied were: i) the electron transport system activity, protein and glycogen contents (indicators of organisms’ metabolic status and energy reserves); ii) lipid peroxidation and the ratio between reduced and oxidized glutathione (indicators of oxidative stress); iii) superoxide dismutase and catalase activities (enzymes indicators of antioxidant defence) and iv) activity of glutathione S-transferases (family of enzymes indicators of biotransformation capacity). Results obtained showed that the uptake of Cd and CBZ was not affected by the combined presence of the contaminants.
However, for CTZ, the uptake was higher in the presence than in the absence of Cd. Concerning toxicity data, in general, the combined exposures (CTZ+Cd, CBZ+Cd) had lower biological effects than the contaminants alone. Nevertheless, our data showed that despite the low concentrations tested, they were enough to exert biological effects that differed between single and combined treatments, evidencing the need to conduct more co-exposure studies to increase the environmental relevance of the gathered data.
Several works evaluated the toxicity of pharmaceutical drugs and climate related changes in invertebrates but few explored the combined effects of both stressors, namely considering their mode of action (MoA). Carbamazepine (CBZ) and cetirizine (CTZ) are pharmaceutical drugs detected in the environment and the toxicity derived from the combined effects of these drugs with ocean acidification (OA) is poorly explored. Thus, the present study investigated the biochemical parameters related to an oxidative stress response and the transcription of genes related to the MoA of CBZ (1.0 mg/L) and CTZ (0.6 mg/L) in the clam Ruditapes philippinarum chronically exposed (28 days) to control (7.8) and low (7.5) pH conditions. The results obtained showed that despite the clams accumulated both drugs, at low pH the clams exposed to CTZ decreased drug concentration and BCF values (CTZ uptake: 2.0 ± 0.5 ng/g fresh weight; BCF: 3.8 ± 0.9) in comparison with clams exposed to control pH (CTZ uptake: 2.9 ± 0.3 ng/g fresh weight; BCF: 5.5 ± 0.6). No oxidative stress was induced by the exposure to CBZ or CTZ at each pH level, but the transcription of several genes related with the MoA (neurotransmission, immunity and biomineralization) was altered by low pH, drug exposure and the combination of both stressors. At both pH conditions, CBZ increased the transcription of GABA receptor gene (neurotransmission) and CTZ led to a decrease of Perlucin gene (biomineralization) transcription. The transcription of MyD88 gene (immunity) decreased at low pH (7.5) combined with drug exposure (CBZ or CTZ). Thus, it was highlighted that the interaction of drug exposure and low pH conditions can change bivalves’ sensitivity to drugs or alter drugs toxicity.
We introduce herein boron-dipyrromethene (BODIPY) dyes as a new class of fluorophores for the design of reporter dyes for supramolecular host–guest complex formation with cucurbit[7]uril (CB7). The BODIPYs contain a protonatable aniline nitrogen in the meso-position of the BODIPY chromophore, which was functionalized with known binding motifs for CB7. The unprotonated dyes show low fluorescence due to photoinduced electron transfer (PET), whereas the protonated dyes are highly fluorescent. Encapsulation of the binding motif inside CB7 positions the aniline nitrogen at the carbonyl rim of CB7, which affects the pKa value, and leads to a host-induced protonation and thus to a fluorescence increase. The possibility to tune binding affinities and pKa values
is demonstrated and it is shown that, in combination with the beneficial photophysical properties of BODIPYs, several new applications of host–dye reporter pairs can be implemented. This includes indicator displacement assays with favourable absorption and
emission wavelengths in the visible spectral region, fluorescence correlation spectroscopy, and noncovalent surface functionalization
with fluorophores.
For metal-based additive manufacturing, sensors and measuring systems for monitoring of the energy source, the build volume, the melt pool and the component geometry are already commercially available. Further methods of optics, spectroscopy and non-destructive testing are described in the literature as suitable for in-situ application, but there are only a few reports on practical implementations.
Therefore, a new BAM project aims to develop process monitoring methods for the in-situ evaluation of the quality of additively manufactured metal components. In addition to passive and active thermography, this includes optical tomography, optical emission and absorption spectroscopy, eddy current testing, laminography, X-ray backscattering and photoacoustic methods. These methods are used in additive manufacturing systems for selective laser melting, laser metal deposition and wire arc additive manufacturing. To handle the sometimes huge amounts of data, algorithms for efficient preprocessing are developed and characteristics of the in-situ data are extracted and correlated to defects and inhomogeneities, which are determined using reference methods such as computer tomography and metallography. This process monitoring and fusion of data of different measurement techniques should result in a significant reduction of costly and time-consuming, destructive or non-destructive tests after the production of the component and at the same time reduce the production of scrap.
Here, first results of simultaneous measurements of optical emission spectroscopy and thermography during the laser metal deposition process using 316L as building material are presented. Temperature values are extracted from spectroscopic data by fitting of blackbody emission spectra to the experimental data and compared with results from a thermographic camera. Measurements with and without powder flow reveal significant differences between welding at a pristine metal surface and previously melted positions on the build plate, illustrating the significant influence of the partial oxidation of the surface during the first welding process on subsequent welding. The measurement equipment can either be mounted stationary or following the laser path. While first results were obtained in the stationary mode, future applications for online monitoring of the build of whole parts in the mobile mode are planned.
This research was funded by BAM within the focus area Material.
The project ProMoAM is presented. The goal of the project is to evaluate which NDT techniques or combination of techniques is suited for in-situ quality assurance in additive manufacturing of metals. To this end, also 3d-data fusion and visualization techniques are applied. Additional ex-situ NDT-techniques are used as references for defect detection and quantification. Feasability studies for NDT-techniques that are presently not applicable for in-situ use are performed as well.
The presentation gives a brief overview of the whole project and the different involved NDT-techniques.
Objectives: Using a murine model of multiple sclerosis, we previously showed that repeated administration of gadopentetate dimeglumine led to retention of gadolinium (Gd) within cerebellar structures and that this process was enhanced with inflammation. This study aimed to compare the kinetics and retention profiles of Gd in inflamed and healthy brains after application of the macrocyclic Gd-based contrast agent (GBCA) gadobutrol or the linear GBCA gadopentetate. Moreover, potential Gd-induced neurotoxicity was investigated in living hippocampal slices ex vivo.
Materials and Methods: Mice at peak of experimental autoimmune encephalomyelitis (EAE; n = 29) and healthy control mice (HC; n = 24) were exposed to a cumulative dose of 20 mmol/kg bodyweight of either gadopentetate dimeglumine or gadobutrol (8 injections of 2.5 mmol/kg over 10 days). Magnetic resonance imaging (7 T) was performed at baseline as well as at day 1, 10, and 40 post final injection (pfi) of GBCAs. Mice were sacrificed after magnetic resonance imaging and brain and blood Gd content was assessed by laser ablation-inductively coupled plasma (ICP)-mass spectrometry (MS) and ICP-MS, respectively. In addition, using chronic organotypic hippocampal slice cultures, Gd-induced neurotoxicity was addressed in living brain tissue ex vivo, both under control or inflammatory (tumor necrosis factor α [TNF-α] at 50 ng/μL) conditions.
Results: Neuroinflammation promoted a significant decrease in T1 relaxation times after multiple injections of both GBCAs as shown by quantitative T1 mapping of EAE brains compared with HC. This corresponded to higher Gd retention within the EAE brains at 1, 10, and 40 days pfi as determined by laser ablation-ICP-MS. In inflamed cerebellum, in particular in the deep cerebellar nuclei (CN), elevated Gd retention was observed until day 40 after last gadopentetate application (CN: EAE vs HC, 55.06 ± 0.16 μM vs 30.44 ± 4.43 μM). In contrast, gadobutrol application led to a rather diffuse Gd content in the inflamed brains, which strongly diminished until day 40 (CN: EAE vs HC, 0.38 ± 0.08 μM vs 0.17 ± 0.03 μM). The analysis of cytotoxic effects of both GBCAs using living brain tissue revealed an elevated cell death rate after incubation with gadopentetate but not gadobutrol at 50 mM. The cytotoxic effect due to gadopentetate increased in the presence of the inflammatory mediator TNF-α (with vs without TNF-α, 3.15% ± 1.18% vs 2.17% ± 1.14%; P = 0.0345).
Conclusions: In the EAE model, neuroinflammation promoted increased Gd retention in the brain for both GBCAs. Whereas in the inflamed brains, efficient clearance of macrocyclic gadobutrol during the investigated time period was observed, the Gd retention after application of linear gadopentetate persisted over the entire observational period. Gadopentetate but not gadubutrol appeared to be neurotoxic in an ex vivo paradigm of neuronal inflammation.
NIR-excitable lanthanide nanocrystals (LnNC) show multi-color emission pattern composed of a multitude of narrow bands of varying intensity in the ultraviolet, visible, near-infrared, and short-wave infrared detectable with miniaturized optical instruments and simple color (RGB) cameras in complex environments. This makes these chemically inert luminescent materials ideal candidates for anticounterfeiting and authentication applications as well as for modules in optical sensors in which the LnNCs can be used as nanolamps in combination with analyte-sensitive fluorophores or the temperature sensitivity of defined emission bands can be utilized.
Therefore, we are building up and exploring a platform of LnNC with application-specifically tuned size, composition, and surface chemistry.
Optical Stability Studies of Hexagonal Upconverting Nanocrystals and Development of Monitoring Tools
(2021)
We demonstrate the potential of time-resolved luminesence spectroscopy for the straightforward assessment and in situ monitoring of the stabilty of UCNPs. Different analytical methods were used to assess the dissolution behaviour of UCNPs in varuous media. Potentiometric and optical data were correlated to develop a new non-invasive monitoring tool for particle dissolution
Assessing dissolution of upconverting nanoparticles by TEM, EDXS, potentiometry and fluorometry
(2021)
Inorganic lanthanide-doped upconversion nanoparticles (UCNP) constitute an emerging class of near-infrared (NIR)-excitable luminescent reporters for bioimaging, fluorescence assays, sensors in bioanalysis, and optical thermometry as well as phosphors for photovoltaic and security applications.1 However, the use of UCNPs in bioimaging and cellular studies requires biocompatible particles. One possible cause of UCNP toxicity is the release of potentially harmful fluoride fluoride and lanthanide ions as revealed by dilution studies in aqueous environments, particularly under high dilution conditions.2-5 To address this issue, suitable surface coatings preventing such effects in combination with fast screening methods suited for online in situ analysis are desired.
Here we present a systematic study of differently sized β-NaYF4:Yb,Er nanocrystals stabilized with different surface coatings and different hydrophilic ligands varying in binding strength to the surface atoms in various aqueous environments at different temperatures.
Functionalisation of UCNPs with analyte-responsive dyes as resonance energy transfer (RET)acceptors, which is in the focus of our work, will yield chemoresponsive nanoprobes with unique features: they can be excited in the NIR range (which minimizes the photo-damage of biological samples, as well as the autofluoresence background) and one of their several sharp UC emission bands can be used as donor for RET sensing applications in combination with analyte-sensitive dyes which serve as indicators, whereas the other UC band(s) can act as internal reference. The first step upon preparation of such nanosensors is the functionalisation of the UCNPs with different surface chemistries for indicator conjugation. Desirable are systems with short distance between the UCNP(donor) and the indicator (acceptor) as a prerequisite for efficient RET. Additionally, dyes with a large spectral overlap between their absorption and one of the UC emission bands are required. Several classes of pH-responsive fluorescent dyes like xanthenes are eligible. Here, we present first studies to optimize the surface functionalization to achieve high RET efficiencies, which would improve the performance of such nanosensors for ratiometric fluorescence measurements of pH in biological matrices.
Lanthanide-based, spectrally shifting, and multi-color luminescent upconverting nanoparticles (UCNPs) have received much attention in the last decades because of their applicability as reporter for bioimaging, super-resolution microscopy, and sensing as well as barcoding and anti-counterfeiting tags. A prerequisite for the broad application of UCNPs in areas such as sensing and encoding are simple, robust, and easily upscalable synthesis protocols that yield large quantities of UCNPs with sizes of 20 nm or more with precisely controlled and tunable physicochemical properties from lowcost reagents with a high reproducibility. In this context, we studied the reproducibility, robustness, and upscalability of the synthesis of β-NaYF4:Yb, Er UCNPs via thermal decomposition. Reaction parameters included solvent, precursor chemical compositions, ratio, and concentration. The resulting UCNPs were then examined regarding their application-relevant physicochemical properties such as size, size distribution, morphology, crystal phase, chemical composition, and photoluminescence.
Based on these screening studies, we propose a small volume and high-concentration synthesis approach that can provide UCNPs with different, yet controlled size, an excellent phase purity and tunable morphology in batch sizes of up to at least 5 g which are well suited for the fabrication of sensors, printable barcodes or authentication and recycling tags.
We present the synthesis and characterization of a family of regioisomerically pure pH-sensitive rosamine fluorophores consisting of xanthene fluorophore cores, which determine the dyes’ photophysical properties such as excitation/emission wavelength, fluorescence quantum yield, and fluorescence lifetime, and differently substituted phenol moieties. The hydroxyl substituent of the phenol moiety introduces a pH sensitivity of the dyes’ fluorescence exploiting a photoinduced electron transfer (PET), that leads to a protonation-induced switching ON of the rosamine emission. Rational tuning of the pKa value of the rosamine fluorescence between 4 to 9 is achieved by altering the substitution pattern and degree of bromination of the phenolic subunits. Additionally, a temperature sensitivity of the fluorescence quantum yield is introduced or suppressed based upon the degree of rigidity of the xanthene scaffold.
We demonstrate the potential of time-resolved luminescence spectroscopy for the straightforward assessment and in situ monitoring of the stability of upconversion nanocrystals (UCNPs). Therefore, we prepared hexagonal NaYF4:Yb3+,Er3+ UCNPs with various coatings with a focus on phosphonate ligands of different valency, using different ligand exchange procedures, and studied their dissolution behaviour in phosphate-buffered saline (PBS) dispersions at 20 °C and 37 °C with various analytical methods. The amount of the released UCNPs constituting fluoride ions was quantified by potentiometry using a Fluoride ion-sensitive electrode and particle disintegration was confirmed by transmission electron microscopy studies of the differently aged UCNPs. In parallel, the luminescence features of the UCNPs were measured with special emphasis on the lifetime of the sensitizer emission to demonstrate its suitability as Screening parameter for UCNP stability and changes in particle composition. The excellent correlation between the changes in luminescence lifetime and fluoride concentration highlights the potential of our luminescence lifetime method for UCNP stability screening and thereby indirect monitoring of the release of potentially hazardous fluoride ions during uptake and dissolution in biological systems. Additionally, the developed in situ optical method was used to distinguish the dissolution dynamics of differently sized and differently coated UCNPs.
Metallic nanoparticles (NPs) are currently applied in a variety of consumer products and are also attractive for medical applications. With their widespread use, the potential for human exposure to NPs — either intended or unintended — is increasing. Therefore, many studies have evaluated the toxicity and transport mechanism of NPs. In comparison with two-dimensional cultured cells, multicellular spheroids (MCS) look promising to be used as a three-dimensional cellular model, having unique advantages in nanoparticle studies due to the fact that interactions with excreted extracellular matrix can be investigated. Fibroblast cells are one of the most important cell systems to express a microenvironment by excreting an abundant extracellular matrix. For bioimaging laser ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS) is used in this investigation to study the interaction of metallic NPs with MCS for multi-element detection offering a wide dynamic range. As a mass spectrometer we have applied a time-of-flight (TOF) instrument for (quasi-) simultaneous detection of all isotopes of elements of interest.
The aim of this study is to investigate the localization of silver (Ag) NPs exposed to fibroblast MCSs by means of LA-ICP-TOF-MS. In addition, for demonstrating elemental microscopy we chose phosphorous (31P) and iron (56Fe) to visualize regions of enriched extracellular matrix and single cells, respectively. In this presentation, we show that exposed Ag NPs are highly accumulated at the same position of single cells in an outer rim of fibroblast MCSs.
We have applied laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) with subcellular resolution as an elemental mass microscope to investigate the distributions of Ag nanoparticles (NP) in a 3-dimentional multicellular spheroid (MCS) model. The production of MCS has been optimized by changing the seeding cell number (500 to 40,000 cells) and the growth period (1 to 10 days). Incubations of MCS with Ag nanoparticle suspensions were performed with a concentration of 5 µg mL-1 for 24 hours. Thin-sections of the Eosin stained MCS were analysed by elemental mass microscopy using LA-ICP-MS to image distributions of 109Ag, 31P, 63Cu, 66Zn and 79Br. A calibration using NP suspensions was applied to convert the measured Ag intensity into the number of particles being present in each measurement pixel. The numbers of NP determined ranged from 30 up to 4,000 particles in an enrichment zone. The particle distribution was clearly correlated to 31P, 66Zn and 79Br and was localized in an outer rim of proliferating cells (confirmed by DAPI) with a width of about two-single cell diameters. For the highest seeding cell number NPs were only detected in this outer rim, whereas small molecules as for instance 79Br and 109Ag ions were detected in the core of the MCS as well. Aniline blue staining demonstrated that this outer rim was rich in collagen structures in which fibroblast cells were embedded and a thin-membrane was visible which separated the core from the biological active cell layer functioning as biological barriers for NP transport. In this presentation, we will show the possibility using this 3-dimensional model for toxicological and medical applications.
We have efficiently produced collagen-rich microstructures in fibroblast multicellular spheroids (MCSs) as a three-dimensional in vitro tissue analog to investigate silver (Ag) nanoparticle (NP) penetration. The MCS production was examined by changing the seeding cell number (500 to 40,000 cells) and the growth period (1 to 10 days). MCSs were incubated with Ag NP suspensions with a concentration of 5 μg/mL for 24 h. For this study, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to visualize Ag NP localization quantitatively. Thin sections of MCSs were analyzed by LA-ICP-MS with a laser spot size of 8 μm to image distributions of 109Ag, 31P, 63Cu, 66Zn, and 79Br. A calibration using a NP suspension was applied to convert the measured Ag intensity into the number of NPs present. The determined numbers of NPs ranged from 30 to 7200 particles in an outer rim of MCS. The particle distribution was clearly correlated with the presence of 31P and 66Zn and was localized in the outer rim of proliferating cells with a width that was equal to about twice the diameter of single cells. Moreover, abundant collagens were found in the outer rim of MCSs. For only the highest seeding cell number, NPs were completely captured at the outer rim, in a natural barrier reducing particle transport, whereas Eosin (79Br) used as a probe of small molecules penetrated into the core of MCSs already after 1 min of exposure.
We applied high resolution laser ablation inductively coupled plasma time-of-flight mass spectrometry (LA-ICP-TOF-MS) with cellular spatial resolution for bioimaging of nanoparticles uptaken by fibroblast multicellular spheroids (MCS). This was used to quantitatively investigate interactions of silver nanoparticles (Ag NPs) and the distributions of intrinsic minerals and biologically relevant elements within thin sections of a fibroblast MCS as a three-dimensional in vitro tissue model. We designed matrix-matched calibration standards for this purpose and printed them using a noncontact piezo-driven array spotter with a Ag NP suspension and multielement standards. The limits of detection for Ag, Mg, P, K, Mn, Fe, Co, Cu, and Zn were at the femtogram (fg) level, which is sufficient to investigate intrinsic minerals in thin MCS sections (20 μm thick). After incubation for 48 h, Ag NPs were enriched in the outer rim of the MCS but not detected in the core. The localization of Ag NPs was inhomogeneous in the outer rim, and they were colocalized with a single-cell-like structure visualized by Fe distribution (pixel size of elemental images: 5 × 0.5 μm). The quantitative value for the total mass of Ag NPs in a thin section by the present method agreed with that obtained by ICP-sector field (SF)-MS with a liquid mode after acid digestion.
We investigated the penetration of silver nanoparticles (Ag NPs) into a three-dimensional in vitro tissue analog using NPs with various sizes and surface coatings, and with different incubation times. A high-Resolution laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) time-of-flight (TOF) instrument was applied for imaging the distributions of elements in thin sample sections (20 μm thick). A fibroblast multicellular spheroid (MCS) was selected as the model system and cultured for more than 8 days to produce a natural barrier formed by the extracellular matrix containing collagen. The MCS was then exposed for up to 48 h to one of four types of Ag NPs (∅ 5 nm citrate coated, ∅ 20 nm citrate coated, ∅ 20 nm polyvinylpyrrolidone coated, and ∅ 50 nm citrate coated). Imaging showed that the penetration pathway was strongly related to steric networks formed by collagen fibrils, and Ag NPs with a hydrodynamic diameter of more than 41 nm were completely trapped in an outer rim of the MCSs even after incubation for 48 h. In addition, we examined the impact of these NPs on essential elements (P, Fe, Cu, and Zn) in
areas of Ag NP accumulation. We observed a linear increase at the sub-femtogram level in the total concentration of Cu (fg per pixel) in samples treated with small or large Ag NPs (∅ 5 nm or ∅ 50 nm) for 48 h.
The suitability of an Al2O3 coating for corrosion protection on X20Cr13 was evaluated in various artificial geothermal brines, focusing on the influence of different pH (4, 6 and 8) and their chemical compositions on the coating properties. All experiments were performed in the laboratory using autoclaves at 150 ◦C and 1 MPa in deaerated condition for 1 and 7 days. Results showed that the pH of geothermal waters is the most detrimental factor in the transformation of ɣ-Al2O3 and its protective abilities. Delaminations were found in the Coating exposed to geothermal brines with pH 4. FTIR spectra indicated a transformation of ɣ-Al2O3 to boehmite AlOOH after exposure to pH 4 and 6, and bayerite Al(OH)3 was formed after exposure to pH 8. Different Crystal structures of the hydrated Al2O3 also contribute to the stability of the coatings, observed by the SEM- EDX of the surface and cross-section of coatings. This study indicated that ɣ-Al2O3 sol-gel coating presents a promising aspect of corrosion protection in geothermal environment with a neutral pH.
Imaging of Eu doped very small iron oxide nanoparticle in atherosclerotic plaques via LA-ICP-MS
(2018)
Atherosclerotic lesions can be visualized by magnetic resonance imaging (MRI) using very small iron oxide nanoparticles (VSOP). VSOP accumulate in atherosclerotic plaques and thus serve as an atherosclerosis probe. The aim of this project was to image the distribution of europium doped VSOP (Eu-VSOP) by laser ablation ICP-MS in histological thin cuts of the aortic root region of ApoE knockout mouse model that is rich in atherosclerotic plaques. In addition, it was investigated whether VSOP accumulation in the plaques correlates with other biomarkers of inflammation for example macrophages and altered endothelium to assess whether it correlates with instability or vulnerability of the plaque regions. For this purpose, antibodies were labeled with various lanthanide elements and correlated with the Eu-VSOP distribution using LA-ICP-MS in a multiplex measurement mode.
Imaging of Eu doped very small iron oxide nanoparticle in atherosclerotic plaques via LA ICP-MS
(2018)
Atherosclerotic lesions can be visualized by magnetic resonance imaging (MRI) using very small iron oxide nanoparticles (VSOP). VSOP accumulate in atherosclerotic plaques and thus serve as an atherosclerosis probe.
The aim of this project was to image the distribution of europium doped VSOP (Eu-VSOP) by laser ablation ICP-MS in histological thin cuts of the aortic root region of ApoE knockout mouse model that is rich in atherosclerotic plaques. In addition, it was investigated whether VSOP accumulation in the plaques correlates with other biomarkers of inflammation for example macrophages and altered endothelium to assess whether it correlates with instability or vulnerability of the plaque regions. For this purpose, antibodies were labeled with various lanthanide elements and correlated with the Eu-VSOP distribution using LA-ICP-MS in a multiplex measurement mode.
A possible correlation of reactive oxygen species (ROS) with endogenous iron or Eu-VSOP can also be detected by LA-ICP-MS. For this purpose, ROS-specific antibodies were also labeled with lanthanides.
Atherosklerotische Läsionen können durch Magnetresonanztomographie (MRT) unter Verwendung von sehr kleinen Eisenoxidnanopartikeln (VSOP) sichtbar gemacht werden. VSOP akkumulieren in atherosklerotischen Plaques und dienen somit als Atherosklerosesonde.
Das Ziel dieses Projektes war die Abbildung der Verteilung von Europium-dotierten VSOP (Eu-VSOP) durch Laserablation ICP-MS in histologischen Dünnschnitten der Aortenwurzelregion des ApoE-Knockout-Mausmodells, das reich an atherosklerotischen Plaques ist. Darüber hinaus wurde untersucht, ob die VSOP-Akkumulation in den Plaques mit anderen Biomarkern der Entzündung wie Makrophagen und verändertem Endothel korreliert. Somit wäre eine Beurteilung, ob es sich hierbei um instabile bzw. vulnerable Plaque-Regionen handelt möglich. Zu diesem Zweck wurden Antikörper mit verschiedenen Lanthaniden markiert und mit der Eu-VSOP-Verteilung unter Verwendung von LA-ICP-MS in einem Multiplex-Messmodus korreliert.
Eine mögliche Korrelation von reaktiven Stickstoffspezies (RNS) mit endogenem Eisen oder Eu-VSOP kann ebenfalls durch LA-ICP-MS nachgewiesen werden. Zu diesem Zweck wurden RNS-spezifische Antikörper auch mit Lanthaniden markiert.
Imaging of Eu doped very small iron oxide nanoparticle in atherosclerotic plaques via LA-ICP-MS
(2018)
Atherosclerotic lesions can be visualized by magnetic resonance imaging (MRI) using very small iron oxide nanoparticles (VSOP). VSOP accumulate in atherosclerotic plaques and thus serve as an atherosclerosis probe.
The aim of this project was to image the distribution of europium doped VSOP (Eu-VSOP) by laser ablation ICP-MS in histological thin cuts of the aortic root region of ApoE knockout mouse model that is rich in atherosclerotic plaques. In addition, it was investigated whether VSOP accumulation in the plaques correlates with other biomarkers of inflammation for example macrophages and altered endothelium to assess whether it correlates with instability or vulnerability of the plaque regions. For this purpose, antibodies were labeled with various lanthanide elements and correlated with the Eu-VSOP distribution using LA-ICP-MS in a multiplex measurement mode.
A possible correlation of reactive nitrogen species (RNS) with endogenous iron or Eu-VSOP can also be detected by LA-ICP-MS. For this purpose, RNS-specific antibodies were also labeled with lanthanides.
Because of the globally increasing prevalence of diabetes, the need for accurate, efficient and at best miniaturized automated analytical systems for sugar detection in medical diagnostics and the food industry is still urgent. The development of molecular probes for sugars based on boronic acid receptors offers an excellent alternative to the kinetically slow enzyme-based sugar sensors. Moreover, by coupling such chelating units with dye scaffolds like BODIPYs (boron–dipyrromethenes), highly fluorescent sugar sensing schemes can be realized. In this work, a boronic acid-functionalized BODIPY probe was developed, which binds selectively to fructose’s adjacent diols to form cyclic boronate esters. Placement of an amino group in direct neighborhood of the boronic acid moiety allowed us to obtain a broad working range at neutral pH, which distinguishes the probe from the majority of systems working only at pH > 8, while still meeting the desired sensitivity in the micro-molar range due to a pronounced analyte-induced fluorescence increase. To enhance the applicability of the test in the sense described above, integration with a microfluidic chip was achieved. Here, fructose was selectively detected by fluorescence with similar sensitivity in real time on chip, and an assay for the straightforward detection of sugar in (colored) sodas without sample clean-up was established.
The allergenic and inflammatory potential of proteins can be enhanced by chemical modification upon exposure to atmospheric or physiological oxidants. The molecular mechanisms and kinetics of such modifications, however, have not yet been fully resolved. We investigated the oligomerization and nitration of the grass pollen allergen Phl p 5 by ozone (O3), nitrogen dioxide (NO2), and peroxynitrite (ONOO–). Within several hours of exposure to atmospherically relevant concentration levels of O3 and NO2, up to 50% of Phl p 5 were converted into protein oligomers, likely by formation of dityrosine cross-links. Assuming that tyrosine residues are the preferential site of nitration, up to 10% of the 12 tyrosine residues per protein monomer were nitrated. For the reaction with peroxynitrite, the largest oligomer mass fractions (up to 50%) were found for equimolar concentrations of peroxynitrite over tyrosine residues. With excess peroxynitrite, the nitration degrees increased up to 40% whereas the oligomer mass fractions decreased to 20%. Our results suggest that protein oligomerization and nitration are competing processes, which is consistent with a two-step mechanism involving a reactive oxygen intermediate (ROI), as observed for other proteins. The modified proteins can promote pro-inflammatory cellular signaling that may contribute to chronic inflammation and allergies in response to air pollution.
Es wurde im Rahmen dieser Arbeit eine neue Methode der Biokonjugation entwickelt, die es ermöglicht humane Antikörper ortspezifisch mit IgG-bindenden Peptiden zu konjugieren. Als Basis fungierte ein Peptid, welches für den Einsatz gezielt modifiziert wurde. So sollte am C-Terminus ein Biotin eingefügt werden, dass für die spätere Detektion der Biokonjugation genutzt werden kann, während am N-Terminus ein Cross-Linker für die kovalente Bindung zum Antikörper eingefügt wurde. Das Biotin wurde mittels Biotin-Lysin eingebaut. Dies hat den Vorteil, dass die modifizierte Aminosäure direkt in der SPPS genutzt werden kann. Auch der Cross-Linker soll schon während der SPPS in das Peptid integriert werden. Als Cross Linker wurden die zwei heterobifunktionellen Succinimidyl(3-bromoacetamid)propionate und Succinimidyl(4-iodacetyl)aminobenzoat untersucht. Die Aktivierung des Peptides mit dem SBAP-Cross-Linker erfolgte am besten im pH-Bereich zwischen 7,0 und 9,0. Die Modifizierung des Peptides mit dem Iodid-Cross-Linker SIAB unter den gleichen Bedingungen zeigte allerdings keine zufriedenstellenden Ergebnisse. Da das erste Peptid allerdings in den Folgeexperimenten sehr gute Ergebnisse zeigte, musste kein weiterer Linker getestet werden. Zusätzlich zu der Cross-Linker-Wahl sollte der Abstand zwischen dem Cross-Linker und dem Grundgerüst des Peptides auf den Einfluss der Bindung untersucht werden. Dazu wurden drei Kontrollpeptide synthetisiert, die entweder um zwei Aminosäuren zwischen dem ursprünglichen N-Terminus des Peptides und dem SBAP-Linker verlängert wurden, keinen SBAP-Linker beinhalten oder die Verlängerung ohne SBAP-Linker besaßen. Die erfolgreiche Synthese aller vier Peptide wurde mittels MALDI-TOF-MS bestätigt.
Cryoadsorption on the inner surface of porous materials is a promising solution for safe, fast, and reversible hydrogen storage. Within the class of highly porous metal−organic frameworks, zeolitic imidazolate frameworks (ZIFs) show high thermal, chemical, and mechanical stability. In this study, we selected ZIF-8 synthesized mechanochemically by twin-screw extrusion as powder and pellets. The hydrogen storage capacity at 77 K and up to 100 bar has been analyzed in two laboratories applying three different measurement setups showing a high reproducibility. Pelletizing ZIF-8 increases the packing density close to the corresponding value for a single crystal without loss of porosity, resulting in an improved volumetric hydrogen storage capacity close to the upper limit for a single crystal. The high volumetric uptake combined with a low and constant heat of adsorption provides ca. 31 g of usable hydrogen per liter of pellet assuming a temperature−pressure swing adsorption process between 77 K − 100 bar and 117 K − 5 bar. Cycling experiments do not indicate any degradation in storage capacity. The excellent stability during preparation, handling, and operation of ZIF-8 pellets demonstrates its potential as a robust adsorbent material for technical application in pilot- and full-scale adsorption vessel prototypes.
Highly selective and sensitive antibodies are only available for a limited number of small molecules. Hence the development of new antibodies is important to exploit the full potential of immunoanalytics. Small molecules do not elicit an immune response in mammals unless conjugated to carrier molecules. The choice of the structures to be conjugated, called haptens, is critical for the antibody production. Here we present our Approach to produce antibodies for the plasticizer diisononyl 1,2-cyclehexane-dicarboxylic acid (DINCH) and di-2-ethylhexyl terephthalate (DEHT) as well as the bile acid isolithocholic acid (ILA).
Studies on the development of antibodies for the highly hydrophobic plasticizers DINCH and DEHT
(2018)
Diisononylcyclohexane-1,2-dicarboxylate (DINCH) and di-2-ethylhexyl terephthalate (DEHT), two of the most important substitutes for phthalate plasticizers, are used for a wide range of applications. Consequently, an increasing occurrence in urine and environmental samples is reported. Reliable and fast analytical methods for the quantification of these plasticizers are needed. So far, mainly GC-MS or LC-MS methods are used. We aimed to develop the first antibodies and immunoassays allowing for high-throughput analysis of samples. We designed two DINCH hapten structures and one DEHT hapten structure and employed hapten-protein conjugates for the immunization of rabbits. Sensitive competitive enzyme-linked immunosorbent assays (ELISAs) against each hapten using the produced polyclonal antibodies were established. Yet, binding of DINCH to the respective antibodies was not observed in neither direct nor indirect assay formats, even when using protein conjugates with the heterologous haptens and different carrier proteins in the indirect format. The use of surfactants and solvents in the sample buffer did not result in recognition of the plasticizers. Also, no binding of DEHT in ELISA employing the respective antibodies was detected. We speculate that the production of antibodies against these highly hydrophobic molecules is not possible via our route, however a different hapten design could overcome this obstacle.
Recent progress has shown that using wavelengths between 1,000 and 2,000 nm, referred to as the shortwave-infrared or near-infrared (NIR)-II range, can enable high-resolution in vivo imaging at depths not possible with conventional optical wavelengths.
However, few bioconjugatable probes of the type that have proven invaluable for multiplexed imaging in the visible and NIR range are available for imaging these wavelengths. Using rational design, we have generated persulfonated indocyanine dyes with absorbance maxima at 872 and 1,072 nm through catechol-ring and aryl-ring fusion, respectively, onto the nonamethine scaffold. Multiplexed two-color and three-color in vivo imaging using monoclonal antibody and dextran conjugates in several tumor models illustrate the benefits of concurrent labeling of the tumor and healthy surrounding tissue and lymphatics.
These efforts are enabled by complementary advances in a custom-built NIR/shortwave-infrared imaging setup and software package for multicolor real-time imaging.
The potential release of hazardous substances from polymer-based products is currently in the focus of environmental policy. Environmental simulations are applied to expose such products to selected aging conditions and to investigate release processes. Commonly applied aging exposure types such as solar and UV radiation in combination with water contact, corrosive gases, and soil contact as well as expected general effects on polymers and additional ingredients of polymer-based products are described. The release of substances is based on mass-transfer processes to the material surfaces. Experimental approaches to investigate transport processes that are caused by water contact are presented. For tailoring the tests, relevant aging exposure types and release quantification methods must be combined appropriately. Several studies on the release of hazardous substances such as metals, polyaromatic hydrocarbons, flame retardants, antioxidants, and carbon nanotubes from polymers are summarized exemplarily. Differences between natural and artificial exposure tests are discussed and demonstrated for the release of flame retardants from several polymers and for biocides from paints. Requirements and limitations to apply results from short-term artificial environmental exposure tests to predict long-term environmental behavior of polymers are presented.
Fluorometric sensing is a versatile approach for trace analysis outside of the laboratory, requiring suitable sensor materials and their integration into sensing devices. The versatility of fluorophores as probes, especially in terms of the possibility to tailor their optical as well as their recognition properties by synthetic modifications in a wide range, renders them as superior active component for the preparation of optical sensor devices. Recent works at BAM in this field include, for example, the detection of nerve gas agents,illustrating impressively the aforementioned benefits of fluorophores in optical sensing applications.
In the interdisciplinary approach presented here, we target hazardous gases such as ammonia, benzene, and hydrogen sulfide, next to others, which pose a major threat to human health and environmental safety and for which the availability of a sensitive and reliable detection method is highly desirable.
The dyes presented follow a “turn-on” fluorescence schematic, which allows for the selective and sensitive detection of the respective gaseous analyte. The immobilization of the probe in polymeric matrices is then the next step toward the fabrication of a prototype device for molecular sensing. Further steps in the project include the assembly of instruments for test-atmosphere generation, the referencing of the sensor system, development and implementation of an optical setup, and the testing of the prototype device under laboratory conditions and in the field.
In this presentation, we give an overview over the recent developments on this topic in our groups, including fluorophore designs investigated for the detection of benzene, ammonia, and hydrogen sulfide as well as approaches for the design of the sensing device.
Fluorometric sensing is a versatile approach for trace analysis outside of the laboratory, requiring suitable sensor materials and their integration into sensing devices. The versatility of fluorophores as probes, especially in terms of the possibility to tailor their optical as well as their recognition properties by synthetic modifications in a wide range, renders them as superior active component for the preparation of optical sensing devices. Recent works at BAM in this field include, for example, the detection of nerve gas agents, illustrating impressively the aforementioned benefits of fluorophores in optical sensing applications.
In the interdisciplinary project presented here, we target hazardous gases such as ammonia, benzene, and hydrogen sulfide, next to others, which pose a major threat to human health and environmental safety and for which the availability of a sensitive and reliable detection method is highly desirable. The dyes presented follow a “turn-on” fluorescence schematic, which allows for the selective and sensitive detection of the respective gaseous analyte. The immobilization of the probe in polymeric matrices is then the next step toward the fabrication of a prototype device for molecular sensing. Further steps in the project include the assembly of instruments for test-atmosphere generation, the referencing of the sensor system, development and implementation of an optical setup, and the testing of the prototype device under laboratory conditions and in the field.
In this presentation, we give an overview over the recent developments on this topic in our groups. Highlights are hydrogen sulfide sensitive, BODIPY based transition metal complexes, which allow for a sensitive as well as selective detection of the toxic gas. In addition, we present a novel class of highly substituted BODIPY derivatives – pocket-BODIPYs – which are of a synthetically high versatility and can readily be modified to create pockets in the periphery of the molecule of defined geometries. This is illustrated on the successful encapsulation of benzene by a pocket-BODIPY derivative, confirmed by X-ray crystallographic analysis as well as by further spectroscopic and analytical methods.
A “turn-on” fluorescence sensing system based on a BODIPY-cobaloxime complex for the detection of H2S in liquid and gas phase was developed. To that aim, two cobaloxime complexes bearing an axial pyridyl-BODIPY ligand were initially evaluated as sensitive fluorescent HS− indicators in aqueous solution. The sensing mechanism involves the selective substitution of the BODIPY ligand by the HS− anion at the cobalt center, which is accompanied by a strong fluorescence enhancement. The selection of a complex with an ideal stability and reactivity profile toward HS− relied on the optimal interaction between the cobalt metal-center and two different pyridyl BODIPY ligands. Loading the best performing BODIPY-cobaloxime complex onto a polymeric hydrogel membrane allowed us to study the selectivity of the probe for HS− against different anions and cysteine. Successful detection of H2S by the fluorescent “light-up” membrane was not only accomplished for surface water but could also be demonstrated for relevant H2S concentrations in gas phase.
In this communication a novel concept for pH sensing is introduced which is specifically adapted to monitor carbonation induced corrosion in concrete structures. The method is based on a ratiometric measurement principle, exploiting the pH sensitive colour switching of thymol blue in the basic pH regime and the emissive properties of two different (Zn)CdSe/ZnS core shell quantum dots. The transition point of thymol blue in a Hydrogel D4 matrix was determined to be at around pH 11.6, which fits ideally to the intended application. Next to the fundamental spectroscopic characterization of the ratiometric response, a new design for a sensor head, suitable for the incorporation into concrete matrices is presented. Toward this, a manufacturing process was developed which includes the preparation of a double layer of polymers containing either thymol blue or a quantum dot mixture inside a porous ceramic tube. Results of a proof-of-priciple performance test of the sensor head in solutions of different pH and in cement specimens are presented, with encouraging results paving the way for future field tests in concrete.
Stability, dissolution, and cytotoxicity of NaYF4‑upconversion nanoparticles with different coatings
(2022)
Upconversion nanoparticles (UCNPs) have attracted considerable attention owing to their unique photophysical properties. Their utilization in biomedical applications depends on the understanding of their transformations under physiological conditions and their potential toxicity. In this study, NaYF4: Yb,Er UCNPs, widely used for luminescence and photophysical studies, were modified with a set of four different coordinatively bound surface ligands, i.e., citrate, alendronate (AA), ethylendiamine tetra(methylene phosphonate) (EDTMP), and poly(maleic anhydride-alt-1-octadecene) (PMAO), as well as silica coatings with two different thicknesses. Subsequently, the aging-induced release of fluoride ions in water and cell culture media and their cytotoxic profile to human keratinocytes were assessed in parallel to the cytotoxic evaluation of the ligands, sodium fluoride and the lanthanide ions. The cytotoxicity studies of UCNPs with different surface modifications demonstrated the good biocompatibility of EDTMP-UCNPs and PMAO-UCNPs, which is in line with the low amount of fluoride ions released from these samples. An efficient prevention of UCNP dissolution and release of cytotoxic ions, as well as low cytotoxicity was also observed for UCNPs with a sufficiently thick silica shell. Overall, our results provide new insights into the
understanding of the contribution of surface chemistry to the stability, dissolution behavior, and cytotoxicity of UCNPs. Altogether, the results obtained are highly important for future applications of UCNPs in the life sciences and bioimaging studies.
Due to their toxicity and widespread application for mining and industrial purposes, cyanides are ranking among the most important inorganic pollutants which should be tested and monitored not only in the aquatic environment, but also in soils and soil-like materials. Reference materials of soils with relevant contents of cyanide to ensure reliable test results of laboratories are rare today.
New certified reference material (CRM) BAM-U116/CGL306 “Cyanide in soil” was produced within a framework of cooperation between Central Geological Laboratory (CGL) of Mongolia and Federal Institute for Materials Research and Testing (BAM) of Germany in 2013-2017.
The CRM BAM-U116/CGL306 represents a mixture of a sandy soil collected from a contaminated former gasworks area in the Berlin region (Germany) and an unpolluted sandy soil from Nalaikh region (Mongolia). The bulk candidate material for this reference material was prepared at CGL CRM Laboratory exclusively destined to the preparation of reference materials and equipped with modern technical equipment. Homogeneity, stability and shelf life were studied in full compliance with ISO Guide 35. The CRM was evaluated as sufficiently homogeneous. Statistical evaluation of certification analysis was performed using software packages SoftCRM and ProLab Plus. Certified value of total cyanide of the CRM is 12.0 mg/kg and expanded uncertainty was assigned as 0.8 mg/kg.
The intended purpose of this material is the verification of analytical results obtained for the mass fraction of total cyanide in soils and soil-like materials applying the standardized procedure ISO 11262:2011. As any reference material, it can also be used for routine performance checks (quality control charts) or validation studies.
Metal tags find application in a multitude of biomedical systems and the combination with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) offers an opportunity for multiplexing. To lay the foundation for an increase of the signal intensities in such processes, we herein present a general approach for efficient functionalization of a well-defined metal oxido cluster [Bi6O4(OH)(4)(SO3CF3)(6)(CH3CN)(6)].2 CH3CN (1), which can be realized by selecting 7mer peptide sequences via combinatorial means from large one-bead one-compound peptide libraries. Selective cluster-binding peptide sequences (CBS) for 1 were discriminated from non-binders by treatment with H2S gas to form the reduction product Bi2S3, clearly visible to the naked eye. Interactions were further confirmed by NMR experiments. Extension of a binding peptide with a maleimide linker (Mal) introduces the possibility to covalently attach thiol-bearing moieties such as biological probes and for their analysis the presence of the cluster instead of mononuclear entities should lead to an increase of signal intensities in LA-ICP-MS measurements. To prove this, CBS-Mal was covalently bound onto thiol-presenting glass substrates, which then captured 1 effectively, so that LA-ICP-MS measurements demonstrated drastic signal amplification compared to single lanthanide tags.
The amount of data generated worldwide is constantly increasing. These data come from a wide variety of sources and systems, are processed differently, have a multitude of formats, and are stored in an untraceable and unstructured manner, predominantly in natural language in data silos. This problem can be equally applied to the heterogeneous research data from materials science and engineering. In this domain, ways and solutions are increasingly being generated to smartly link material data together with their contextual information in a uniform and well-structured manner on platforms, thus making them discoverable, retrievable, and reusable for research and industry. Ontologies play a key role in this context. They enable the sustainable representation of expert knowledge and the semantically structured filling of databases with computer-processable data triples.
In this perspective article, we present the project initiative Materials-open-Laboratory (Mat-o-Lab) that aims to provide a collaborative environment for domain experts to digitize their research results and processes and make them fit for data-driven materials research and development. The overarching challenge is to generate connection points to further link data from other domains to harness the promised potential of big materials data and harvest new knowledge.
Zinc ferrite and graphene composites have attracted considerable attention in wastewater treatment. In this work, a magnetically separable mesoporous composite of ZnFe2O4 nanoparticles (NPs) and reduced graphene oxide (rGO) was prepared through a simple and eco-friendly method with pure water as solvent and without the need for subsequent thermal treatment. Uniformly dispersed ZnFe2O4 NPs on the surface of rGO sheets exhibited good crystallinity and a large BET specific surface area. These factors contributed to good photocatalytic performance of the composite for the degradation of methylene blue (MB) under simulated solar-light radiation, increased adsorptivity, increased separation efficiency of the photo-excited charges on the surface of the catalyst, and broadened light-absorption range of the composite. Efficient interfacial interaction between the ZnFe2O4 NPs and rGO sheets resulted in synergistic effects. The magnetically separable ZnFe2O4@rGO nanocomposite proved an efficient and stable catalyst in three consecutive photodegradation cycles for MB dye in aqueous solution under solar radiation. In addition, the synthesis method proposed in this study could be scaled-up easily due to the simplicity of the process, the lack of a toxic reagent, and the use of low temperatures.
Das Ziel der vorliegenden Arbeit war die rekombinante Herstellung der AnFAO in E. coli, welche ursprünglich von A. niger produziert wird, und deren anschließende Anwendung in der Entwick-lung eines Fumonisin- Biosensors für die Lebensmittelanalytik. In Bezug auf die aktuell steigen-den Lebensmittel- und Rohstoffpreise ist die Entwicklung eines Schnelltestsystems zur Detektion von Kontaminationen mit Mykotoxinen besonders gefragt, da zusätzliche Verluste und Kosten verhindert werden können. Für die Herstellung der AnFAO als MBP-Fusionsprotein und Biotin-Fusionsprotein mit zusätzlichem 6x His-Tag wurden die pET-MBP-AnFAO und pRSET-BH6-An-FAO Expressionsvektoren erfolgreich konstruiert. Die lösliche Expression im Cytoplasma wurde von MBP-AnFAO erreicht, wobei die Expression von BH6-AnFAO in inclusion bodies erfolgte und keine Aktivität des Enzyms nachgewiesen wurde. Die Enzymaktivität von MBP-AnFAO wurde im optischen Assay und amperometrisch durch die Detektion von H2O2 ermittelt. Im optischen Assay wurde die maximale spezifische Aktivität von 2,45 U/mg bei 45 °C, einer Enzymkonzentration von 3 μM und 50 μM FB1 erreicht. Generell wurden mit FB1 als Enzymsubstrat höhere Fluoreszenzsig-nale und dementsprechend höhere Enzymaktivitäten als für FB2 beobachtet. Es wurde ein linearer Zusammenhang der Enzymaktivitäten mit der Substratkonzentration beobachtet. Außerdem wurde ein Anstieg der H2O2-Konzentration mit zunehmender Inkubationszeit (bis zu 60 Minuten) erkannt. Des Weiteren wurde der Einfluss des MBP-Fusionsproteins auf die Enzymaktivität des AnFAO untersucht. Dabei wurde anhand von wesentlich geringeren Aktivitäten für AnFAO allein ein eventueller Einfluss des MBP auf dessen Aktivität festgestellt. Ein elektrochemischer Aufbau wurde zur Entwicklung eines Fumonisin- Sensors genutzt. Dazu wurde nachgewiesen, dass FB1 von rekombinant hergestelltem MBP-AnFAO unter Bildung von NH3 und H2O2 zu weniger toxi-schem FB1, dem FPy1, oxidiert werden kann. An der PB/Kohlenstoff-Elektrode, welche sensitiver gegenüber H2O2 und stabiler als die CoPC/Kohlenstoff Elektrode war, wurde die Reduktion des enzymatisch gebildeten H2O2 gemessen. Die Erstellung einer FB1- Kalibriergerade mit FB1- Lösun-gen verschiedener Konzentrationen zeigte, dass das Enzym auch in immobilisierter Form in der Lage ist unterschiedliche Konzentrationen an FB1 zu desaminieren. Dazu gehört auch der Kon-zentrationsbereich unterhalb des festgelegten Grenzwertes von 2,7 μmol/kg für Fumonisin. Die amperometrischen Kurven hierfür wurden an der PB/Kohlenstoff-Elektrode erfolgreich aufge-nommen. Störungen des H2O2- Redoxstroms durch das Enzym, der Enzymsubstrate und der Ne-benprodukte während der amperometrischen Messung wurden ausgeschlossen. Sowohl im opti-schen als auch im amperometrischen Assay wurde ausschließlich das enzymatisch gebildete H2O2 bestimmt.
Ein Vergleich der Gehalte von Difluoressigsäure (DFA) und Trifluoressigsäure (TFA) in Regen- und Oberflächenwässern im Berliner Raum ergab ein TFA/DFA Verhältnis in Regenwasser von 10:1. Im Gegensatz dazu wies Grundwasser aus dem Einzugsbereich einer historischen Kontamination durch Fluorchlorkohlenwasserstoffe (FCKW) ein TFA/DFA-Verhältnis von 1:3 auf. Dies und die ungewöhnlich hohe DFA-Konzentration an dieser Stelle wird vor dem Hintergrund der beobachteten mikrobiellen Abbauprodukte des ursprünglichen eingetragenen FCKW 1,1,2-Trichlor-1,2,2-trifluorethan (R113) diskutiert. Eine mikrobielle Umwandlung des bekannten Abbauproduktes Chlortrifluorethylen (R1113) zur DFA wurde bislang nicht in Umweltkompartimenten beobachtet und wird hier auf Basis bekannter Stoffwechselwege vorgeschlagen.
TFA wurde in Regenwasser, Oberflächenwasser und Grundwasser in vergleichbaren Größenordnungen von ca. 500 ng/L bestimmt. Im Gegensatz dazu wurde DFA in Grundwasserproben im Bereich der Schadstoffquelle der FCKW-Kontamination mit bis zu 2.000 ng/L nachgewiesen. Die Summe von TFA und DFA im Grundwasser korreliert nicht mit dem Eintrag aus Niederschlag und Oberflächenwasser. Darum liegt die Vermutung nahe, dass es für DFA andere Quellen als den direkten Eintrag oder den möglichen Abbauweg über TFA geben muss. DFA ist vermutlich ein Abbauprodukt von R1113. FCKWs, die im ersten Abbauschritt zu 1,1-Difluorethenen metabolisieren, stehen im Verdacht, in der Folge zu DFA zu hydrolysieren. Entscheidend scheint, dass bereits im Ausgangsprodukt ein CF2-Strukturelement enthalten ist, das dann zur Bildung von DFA führen kann. Somit würde aus dem ursprünglichen Eintrag des Kältemittels R113 über schrittweise Dechlorierung via 1,2-Dichlor-1,2,2-Trifluorethan (R123a) und R1113 die Bildung des beobachteten DFA folgen. Es ist also sinnvoll, DFA in die Diskussion zur Regulierung der Endprodukte des Abbaus fluorhaltiger Kälte- oder Lösungsmittel einzubeziehen. Die Ergebnisse wurden im Normausschuss Wasserwesen (NAW) des DIN vorgestellt und es soll ein Arbeitskreis gegründet werden, der ein Normverfahren zur Quantifizierung von TFA und DFA in Wasser erarbeitet. Interessierte Laboratorien sind herzlich eingeladen, die Normungsarbeit zu unterstützen.
Nach einer Erläuterung der international üblichen Definitionen von Referenzmaterialien und Matrix-Referenzmaterialien erfolgt eine Zusammenfassung der spezifischen Anforderungen bei Herstellung und Charakterisierung. Weiterhin werden die unterschiedlichen Anforderungen an die Durchführung von Ringversuchen im Sinne eines Methodenvergleiches, einer Eignungsprüfung von Laboratorien und der Zertifizierung von Matrix-Referenzmaterialien gegenübergestellt. Für den aktuell geplanten ersten Ringversuch zur Quantifizierung von Mikroplastik in Schwebstoffen mittels thermischer Verfahren werden die konkreten technischen Bedingungen zur Herstellung entsprechender Referenzmaterialien einschließlich der Homogenitätsprüfung ihrer Mikroplastikgehalte dargestellt. Die Besonderheiten des Ringversuches vor dem Hintergrund einer Normung der eingesetzten Verfahren werden diskutiert.
The pollution of marine, limnic and terrestrial environments with plastic waste and the potential impact especially on biota and humans has received increasing attention in recent years. Special focus is on particles smaller than 5 mm, the so-called microplastics. Consequently, possible regulations of emission and remediation efforts require sound information on the occurrence and fate of microplastics in the respective environmental compartments.
Microplastics (MP) differ from classical organic pollutants in biota or the environment in that they do not consist of clearly defined low-molecular weight compounds but of polymer particulates with varying sizes and chemical compositions. This leads to specific challenges regarding the analytical techniques to be employed for their identification and quantification.
Microplastics are defined as polymer particle in the size range between 1 µm and 5 mm and cover a wide range of polymers such as polyethylene, polypropylene, polystyrene and polyethylene terephthalate in variable geometric shapes. Properties relevant for environmental microplastics are polymer type, particle form and size distribution, surface morphology (aging status) and total mass fraction contained in a given sample. Polymer identification and particle size estimation using optical methods (IR and Raman spectroscopy) are time consuming and complicated by surface characteristics as a result of weathering, soiling, and microbial colonisation. Total mass fractions of MP in environmental samples can be determined by thermo-analytical methods.
There are currently no standardised methods for sampling, sampling preparation, or detection of MP in environmental samples. So far, qualitative and quantitative investigations are done by research institutes and have not reached the routine laboratory community. The near future will see harmonisation efforts of MP mass fraction determination in environmental matrices by thermo-analytical procedures.
The immediate need for reference materials during method development and comparison is outlined with regard to relevant matrix/polymer compositions, existing regulations and currently achievable detection limits. Examples for solid environmental matrix reference materials are discussed regarding the challenges encountered with matrices and polymer types as well as homogeneity testing and property value characterisation.