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Luminescence techniques are amongst the most commonly used analytical methods in life and material sciences due to their sensitivity and their nondestructive and multiparametric character. Photoluminescence signals are, however, affected by wavelength, polarization and time dependent instrument specific effects, and provide only relative intensities. This hampers the comparability of fluorescence measure-ments and calls for simple tools for instrument characterization and the quantification of measured fluorescence intensities. Well characterized fluorescence standards for instrument calibration and performance validation (IPV) can be used as references for fluorescence signals. Of special importance is the correct determination of photoluminescence quantum yields (QF) (number of emitted per absorbed photons) that provides a direct comparison of the fluorescence efficiency of emitters. Such well characterized standards have been successfully developed by BAM for the relative determination of f values of transparent solutions of molecular and nanoscale emitters in the wavelength range from 350 and 1100 nm and will be soon certified. These standards can also be used to evaluate integrating sphere setups, which are increasingly being used for absolute measurements of QF values.
Digital holographic cytometry (DHC) is a state-of-the-art quantitative Phase imaging (QPI) method that permits time-lapse imaging of cells without induced cellular toxicity. DHC platforms equipped with semi-automated image segmentation and analysis software packages for assessing cell behavior are commercially available. In this study we investigate the possible uptake of nanoprobes in macrophages in vitro over time.
Single-particle inductively coupled plasma mass spectrometry (sp-ICP-MS) has become an effective tool for the detection and quantification of inorganic nanoparticles (NPs). While sizing of NPs suspended in water is relatively straightforward by sp-ICP-MS, accurate mass quantification of NPs in complex media, such as consumer products and natural systems still remains a challenge. When NPs are suspended in a complex medium, the matrix may affect the analyte sensitivity and lead to inaccurate NP sizing. Here, we investigate the use of an online microdroplet calibration system to size NPs in a single step. In this setup, microdroplets—which are used as the calibrant to determine elemental sensitivities—and nebulized NP-containing solutions are introduced concurrently into the ICP via a dual-inlet sample introduction system. Because calibrant microdroplets and analyte NPs experience the same plasma conditions, both the microdroplets and the NPs are subjected to the same matrix-related signal enhancement or suppression. In this way, the microdroplet calibration standards are automatically matrix matched with the NP-containing solution. The online microdroplet calibration system is combined with an ICP-TOFMS instrument for simultaneous measurement of multiple elements in microdroplets and NPs. We investigate the ability of online microdroplet calibration to compensate for matrix effects through a series of experiments, in which Ag and Au NPs are measured with variable plasma-sampling positions, varying concentrations of HCl and HNO3, varying concentrations of single element solutions, and high concentrations of a salt matrix, i.e. phosphate buffered saline (PBS). Through these experiments, we demonstrate that the online microdroplet calibration strategy provides a matrix-independent mass quantification of analyte NPs in the presence of several established types of matrix effects, including acid effects, space-charge effects, and ionisation suppression. In results presented here, we focus on the size determination of the NPs.
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is nowadays an established multi-elemental analysis and mapping technique. It was shown that LA-ICP-MS can visualize the elemental distribution within tissue thin sections or cell samples. Quantification is possible by using appropriate matrix-matched calibration samples. Besides naturally occurring elements and metals from contrast agents, biomolecules using metal-tagged antibodies were detected in different bio-medical samples. By combining the results with findings from histology, magnetic resonance imaging (MRI) and other techniques disease related changes like alterations of the extracellular matrix can be investigated.
Screening of one-bead-one-peptide libraries is a powerful analytical tool for the identification of protein ligands. However, the traditional peptide screening procedure involves tedious steps such as manual selection, sequencing, and characterization. We present a high-throughput “all in one chip” system, allowing the screening of a high number of resin beads in short time. Here, beads of a combinatorial one-bead one compound peptide library are immobilized on an in-house produced chip, on which every bead has a well-defined position. The chip is then incubated with a fluorophore-labeled protein, identifying suitable peptides by a high-resolution fluorescence scan. The screening is followed by MALDI-MS experiments directly on the respective glass chip. To circumvent the need for peptide fragmentation normally used for peptide de novo sequencing, which can result in incomplete sequence information, an approach based on ladder sequencing has been used. This allows the peptide sequence identification by fragmentation-free MS with almost 100 % accuracy. For this purpose, a software tool was developed automatically translating MALDI-MS spectra into the corresponding peptide sequences.
In the past, δ26/24Mg measurements were referenced to NIST SRM 980, the initial zero of the δ26/24Mg scale. With the development of MC-ICPMS, the detection of small but measurable isotopic differences in different chips of SRM 980 became apparent. To solve this problem a suite of magnesium isotope reference materials, ERM-AE143, -AE144 and -AE145, has been certified in a first study by applying an ab initio calibration for absolute Mg isotope ratios without any a priori assumptions, a procedure which fulfils all requirements of a primary method of measurement. We could achieve for the first time measurement uncertainties for isotope amount ratios close to the typical precision of magnesium delta values, δ26/24Mg, which are at the 0.1 ‰ level (2SD). In addition, it was demonstrated that commonly used fractionation laws are invalid for correcting Mg isotope ratios in multi-collector ICPMS as they result in a bias which is not covered by its associated uncertainty. Depending on their type, fractionation laws create a bias up to several per mil, with the exponential law showing the smallest bias between 0.1 ‰ to 0.7 ‰.
With these isotope reference materials, it is possible to establish SI-traceability for magnesium delta measurements. To realize this, we organized a second study within which five expert laboratories participated to cross-calibrate all available magnesium isotope standards, which are NIST SRM 980, IRMM-009, ERM-AE143, ERM-AE144, ERM-AE145 and the standards DSM3 and Cambridge-1. The mean δ26/24Mg values for the individual iRMs, calculated from the laboratory means show 2 SD reproducibilities varying between 0.025 and 0.093 ‰. Propagated measurement uncertainties suggest a standard uncertainty of about 0.1‰ for δ26/24Mg determinations (2SD). Thus, SI traceability for magnesium isotope amount ratios and delta values is demonstrated to be established.
Si isotope fractionation during BIF formation – inferences from a modern Archean ocean analogue
(2019)
Silica-rich sedimentary rocks like cherts and BIFS, typical for the Archean, have been used to reconstruct temperatures and other properties of the early oceans through the study of their Si isotope variations. Precambrian cherts and BIFS span a δ30Si range of ~7‰, with BIFs being about 2‰ lower in δ30Si than cherts. These lower δ30Si signatures have been attributed to represent contributions from different input sources such as hydrothermal fluids, variable continental weathering regimes or sorption onto Fe oxides/hydroxides [e.g. 2 and references therein]. In this study, fluids and BIF-like sediments have been investigated for their Si isotope compositions in Paulina Lake (PL), a hydrothermally-influenced crater lake in the Newberry Caldera, Oregon, USA. PL lake sediments are rich in silica (~65wt% SiO2) and are composed of up to 22.5wt% Fe2O3, which is comparable to Archean BIFs and thus serve as a modern Archean ocean analogue. We compared our analyses with East Lake (EL), the twin Newberry crater lake without hydrothermal input. Dissolved Si in EL has an average δ30Si signature of +1.55±0.16‰ (1sd) and sediments an average δ30Si signature of +0.18±0.28‰ (1sd). Dissolved Si in PL has an average δ30Si signature of +2.02±0.15‰ (1sd), whereas the sediments show a large range in δ30Si values between +0.59‰ and -1.24‰. PL sediments show a trend towards more negative δ30Si with increasing Fe2O3 contents. The magnitude of Si isotope fractionation thus appears to depend on the presence of Fe. This fractionation induced by interaction with Fe precipitation is defined here as the offset in δ30Si between PL and EL sediments at comparable depths (Δ30SiPL-EL). The resulting Δ30SiPL-EL values range between +0.69 and -1.42‰ and increase with increasing Fe2O3 content in the sediments. Our results are the first to quantify the magnitude of Fe-induced δ30Si fractionation observed in a natural analogue of the Archean ocean and can explain the lighter δ30Si signatures found in BIFs.
Time-resolved flow cytometry
(2019)
The fast identification of a large number of analytes or events is increasingly required in bioanalytical, diagnostic, and security applications. The versatility and straightforward use make multiparametric fluorescence techniques particularly interesting as detection techniques. An established method for high-throughput single-cell and single-particle measurements is flow cytometry (FCM). Using only spectral encoding without further intensity information, state-of-the-art instruments equipped with several light sources and detectors can resolve almost 20 different color codes. However, this is not sufficient to answer complex research questions, e.g. in cell biology and immunology. In contrast, routine applications demand low-cost and sometimes even portable instruments and thus a minimum number of instrument components. Thus, there are currently two main research directions in FCM: the development of methods that can either address increasingly complex analytical challenges or provide low-cost and robust approaches for routine multiplex analyses. Common spectral multiplexing approaches face limitations in both directions. On the one hand, spectral overlap of labels restricts the number of codes and makes elaborate correction schemes necessary. On the other hand, even for lower degrees of multiplexing often a sophisticated optical setup is needed. An alternative to spectral multiplexing and intensity encoding is to exploit the luminescence lifetime (LT) as an encoding parameter. This can allow for extending the parameter space in combination with spectral encoding or result in more simple and compact devices due to fewer optical components. The availability of fast electronics enables miniaturized and portable lifetime measurement setups at relatively low cost. LT-FCM requires to master LT determination with a limited number of detected photons due to the short interaction time of the encoded objects with the laser spot. In this study, we address this issue for time-domain cytometry and present a novel lifetime flow cytometry (LT-FCM) platform based on a compact setup and straightforward time-domain measurements utilizing LT-encoded luminescent beads. Moreover, we present the realization of a first bioanalytical assay with LT-encoded beads.
The knowledge of transformation pathways and identification of transformation products (TPs) of veterinary drugs is important for health, food and environmental matters. Monensin (MON) is an ionophore antibiotic widely used to cure and prevent coccidiosis by chicken especially in broiler farming. Residues are not only found in food products (chicken and eggs) but also in the environment (manure, soil or water). Several transformation processes can alter the parent compound MON, ranging from biotransformation in living organism to biotic/abiotic and microbial processes in environmental matters.
The main objective of this work was to investigate the potential of electrochemistry (EC) to simulate oxidative transformation processes and to predict TPs of MON. An electrochemical reactor was used consisting of a flow-through cell with a glassy carbon working electrode. Derived TPs were analyzed by online coupling of EC and high-resolution mass spectrometry (HRMS) and LC-HRMS offline measurements. Among the generated TPs already known as well as unknown TPs of MON could be found.
Additionally, MON was subjected also to other transformation methods such as Fenton reaction, photochemical and hydrolysis experiments as well as metabolism tests with microsomes. As a result, different targeted and suspected TPs could be identified by analysis with LC-HRMS.
An overview of detected/identified TPs from this study will be presented in comparison to literature known metabolites and TPs.
Due to its advantages of being a direct comparison method, quantitative NMR spectroscopy (qNMR) becomes more and more popular in industry. While conventional high-field NMR systems are often associated with high investment and operational costs, the upcoming market of permanent-magnet based benchtop NMR systems show a considerable option for a lot of applications. The mobility of these systems allows to bring them more closely to the real production environment, e.g. for at-line quality control.
In this work we present an interlaboratory comparison study investigating the qNMR performance of state-of-the-art benchtop NMR spectrometers. Therefore, BAM prepared two samples of a mixture of NMR reference standards tetramethylbenzene (TMB) and tetrachloronitrobenzene (TCNB) at concentration levels of 200 mM and 10 mM. These “ready-to-use” samples were sent to participant laboratories, which performed analysis on their benchtop NMR equipment of different vendors and fields from 43 to 80 MHz. Raw data was reported back and further investigated by using different data analysis methods at BAM.
After this very first qNMR comparison study of benchtop NMR spectrometers show promising results, following studies are planned to cover more parts of the qNMR process, e.g. sample preparation and weighing, but also data analysis, as commonly done in similar studies for high-field NMR spectroscopy in industry and metrology.
Working towards a comprehensive understanding of introduction pathways, number, and fate of micro¬plastics in the environment, suitable analytical methods are a precondition. Micro-spectroscopic methods are probably the most widely used techniques. Besides their ability to measure single spectra of a particle or fiber, most modern FTIR- and Raman microscopes are also capable of two-dimensional imaging. This is very appealing to microplastics research because it allows to simultaneously characterize the analytes chemically as well as their size (distribution) and shape.
Two-dimensional imaging on extensive sample areas with FTIR-micros¬copes is facilitated by focal plane array (FPA) detectors resulting in large data sets comprised of up to several million spectra. With numbers too large for manual inspection of each individual spectrum, automated data evaluation is inevitable. Identifying different polymers based on the comparison with known reference spectra (library search) has proven to be a suitable approach. For that purpose, FTIR-spectra of common plastics can be collected to create an individual reference library.
To Supplement this ‘targeted analysis’, looking for known substances via library search, an exploratory approach was tested. Principal component analysis (PCA) proved to be a helpful tool to drastically reduce the size of the data set while maintaining the significant information. Subsequently, cluster analysis was used to find groups of similar spectra. Spectra found in different clusters could be assigned to different polymer types. The variation observed within clusters gives a hint on chemical variability of microplastics of the same polymer found in the sample. Spectra labeled according to the respective cluster/polymer type were used to build a classification model which allowed to quickly predict the polymer type based on the FTIR spectrum. Classification was tested on a second, independent data set and results were compared to the spectral library search procedure.
The DNA origami technique has great potential for the development of brighter and more sensitive reporters for fluorescence based detection schemes such as a microbead-based assay in diagnostic applications. The nanostructures can be programmed to include multiple dye molecules to enhance the measured signal as well as multiple probe strands to increase the binding strength of the target oligonucleotide to these nanostructures. Here we present a proof-of-concept study to quantify short oligonucleotides by developing a novel DNA origami based reporter system, combined with planar microbead assays. Analysis of the assays using the VideoScan digital imaging platform showed DNA origami to be a more suitable reporter candidate for quantification of the target oligonucleotides at lower concentrations than a conventional reporter that consists of one dye molecule attached to a single stranded DNA. Efforts have been made to conduct multiplexed analysis of different targets as well as to enhance fluorescence signals obtained from the reporters. We therefore believe that the quantification of short oligonucleotides that exist in low copy numbers is achieved in a better way with the DNA origami nanostructures as reporters.
Organic fluorophores, particularly stimuli-responsive molecules, are very interesting for biological and material sciences applications, but frequently limited by aggregation- and rotation-caused photoluminescence quenching. A series of easily accessible bipyridinium fluorophores, whose emission is quenched by a twisted intramolecular charge-transfer (TICT) mechanism, is reported.
Encapsulation in a cucurbit[7]uril host gave a 1:1 complex exhibiting a moderate emission increase due to destabilization of the TICT state inside the apolar cucurbituril cavity. A much stronger fluorescence enhancement is observed in 2:2 complexes with the larger cucurbit[8]uril, which is caused by additional conformational restriction of rotations around the aryl/aryl bonds. Because the cucurbituril complexes are pH switchable, this system represents an efficient supramolecular ON/OFF fluorescence switch.
Xenobiotics and their reactive metabolites are conjugated with native biomolecules such as glutathione and glucoside during phase II metabolism. Toxic metabolites are usually detoxified during this step. On the other hand, these reactive species have a potential health impact by disrupting many enzymatic functions. Thus, it is crucial to understand phase II conjugation reactions of xenobiotics in order to address their fate and possible toxicity mechanisms.
Additionally, conventional methods (in vivo and in vitro) have limitation due to matrix complexity and time-consuming. Hence, developing fast and matrix-free alternative method is highly demandable. In this work, oxidative phase I metabolites and reactive species of chlorpyrifos (insecticide) and fluopyram (fungicide) were electrochemically produced by using a boron-doped diamond electrode coupled online to electrospray mass spectrometry (ESI-MS). Reactive species of the substrates were trapped by biomolecules (glutathione and glucoside) and phase II conjugative metabolites were identified using liquid chromatography (LC)-MS/MS, and/or Triple time of flight (TripleTOF)-MS. Glutathione conjugates and glucosylation of chlorpyrifos, trichloropyridinol, oxon, and monohydroxyl fluopyram were identified successfully. Glutathione and glucoside were conjugated with chlorpyrifos, trichloropyridinol, and oxon by losing a neutral HCl. In the case of fluopyram, its monohydroxyl metabolite was actively conjugated with both glutathione and glucoside. In summary, seven bioconjugates of CPF and its metabolites and two bioconjugates of fluopyram metabolites were identified using electrochemistry (EC)/MS for the first time in this work. The work could be used as an alternative approach to identify glutathione and glucosylation conjugation reactions of other organic compounds too. It is important, especially to predict phase II conjugation within a short time and matrix-free environment.
A goal of this work is to extend the model, which was initially developed for laser induced plasmas, to plasmas used in chemical reactors, in particular, the inductively-coupled-RF discharge plasma. The model predicts equilibrium chemical compositions of reaction mixtures as functions of plasma temperature and stoichiometry of reactants. The mixtures investigated are BCl3/H2/Ar and BF3/H2/Ar where Ar serves as the plasma-forming gas and H2 as a binding agent which binds the active species Cl and F and Cl- and F-containing intermediates to produce gaseous B and its condensate. An additional goal is to obtain information about intermediate reaction products for different ratios of BCl3/H2 and BF3/H2 and at different temperatures and different Ar flow rates.
It is found that the desired components B and B2 appear at appreciable concentrations of >0.1% and ~0.01% respectively only at temperatures above 3000 K. It is also established that the effect of charged species on the reaction products is miniscule for temperatures below 5000 K. The expected yield of boron as a function of the original mole fraction H2/BCl3 and H2/BF3 is calculated. The mole fractions are varied in the range 0.1-1000 and the temperature in the range 1000-10000 K. It is shown that the yield of boron increases with increasing the molar ratio H2/BCl3 and H2/BF3 up to ~100 in the temperature range 2000-5000 K. At higher temperatures, T>5000 K, the boron concentration reaches its maximum and does not depend on the concentration of hydrogen; all molecules dissociate and chemical reactions proceed only between charged particles (mostly elemental ions) and electrons. The calculated plasma parameters and composition are compared with experimental data obtained by optical emission spectroscopy. The calculated plasma temperature and electron density are shown to be in good agreement with the measured ones.
High purity halides of III-VI group elements, especially chloride and fluorides, are used in gas phase technologies for obtaining high purity materials and coatings. The reduction of halides in hydrogen-halide mixtures can be achieved in various discharge plasmas, e.g. inductively coupled, ark, and even laser-induced plasmas. Existing models of such plasmas are not sufficiently accurate to predict a yield of the targeted compounds and to describe the plasma processes involved in formation of these compounds. Besides, a construction of costly plasma-chemical reactors can be alleviated by the prior modeling of plasma processes that may occur in such reactors.
A goal of this work is to extend the model, which was initially developed for laser induced Plasmas, to plasmas used in chemical reactors, in particular, the inductively-coupled-RF discharge Plasma. The model predicts equilibrium chemical compositions of reaction mixtures as functions of plasma temperature and stoichiometry of reactants. The mixtures investigated are BCl3/H2/Ar and BF3/H2/Ar where Ar serves as the plasma-forming gas and H2 as a binding agent which binds the active species Cl and F and Cl- and F-containing intermediates to produce gaseous B and its condensate. An additional goal is to obtain information about intermediate reaction products for different ratios of BCl3/H2 and BF3/H2 and at different temperatures and different Ar flow rates.
It is found that the desired components B and B2 appear at appreciable concentrations of >0.1% and ~0.01% respectively only at temperatures above 3000 K. It is also established that the effect of charged species on the reaction products is miniscule for temperatures below 5000 K. The expected yield of boron as a function of the original mole fraction H2/BCl3 and H2/BF3 is calculated. The mole fractions are varied in the range 0.1-1000 and the temperature in the range 1000-10000 K. It is shown that the yield of boron increases with increasing the molar ratio H2/BCl3 and H2/BF3 up to ~100 in the temperature range 2000-5000 K. At higher temperatures, T>5000 K, the boron concentration reaches its maximum and does not depend on the concentration of hydrogen; all molecules dissociate and chemical reactions proceed only between charged particles (mostly elemental ions) and electrons. The calculated plasma parameters and composition are compared with experimental data obtained by optical emission spectroscopy. The calculated plasma temperature and electron density are shown to be in good agreement with the measured ones.
Nanomaterials are used in many different applications in the material and life sciences. Examples are optical reporters, barcodes, and nanosensors, magnetic and optical contrast agents, and catalysts. Due to their small size and large surface area, there are also concerns about their interaction with and uptake by biological systems. This has initiated an ever increasing number of cyctoxicity studies of nanomaterials of different chemical composition and surface chemistry, but until now, the toxicological results presented by different research groups often do not address or differ regarding a potential genotoxicity of these nanomaterials. This underlines the need for a standardized test procedure to detect genotoxicity.1,2
Aiming at the development of fast, easy to use, and automatable microscopic methods for the determination of the genotoxicity of different types of nanoparticles, we assess the potential of the fluorometric γH2AX assay for this purpose. This assay, which can be run on an automated microscopic detection system, relies on the determination of DNA double strand breaks as a sign for genotoxicity.3 Here, we present first results obtained with broadly used nanomaterials like CdSe/CdS and InP/ZnS quantum dots as well as iron oxide, gold, and polymer particles of different surface chemistry with previously tested colloidal stability. These studies will be also used to establish nanomaterials as positive and negative genotoxicity controls or standards for assay performance validation for users of this fluorometric genotoxicity assay. In the future, after proper validation, this microscopic platform technology will be expanded to other typical toxicity assays.
References. (1) Landsiedel, R.; Kapp, M. D.; Schulz, M.; Wiench, K.; Oesch, F., Reviews in Mutation Research 2009, 681, 241-258. (2) Henriksen-Lacey, M.; Carregal-Romero, S.; Liz-Marzán, L. M., Bioconjugate Chem. 2016, 28, 212-221. (3) Willitzki, A.; Lorenz, S.; Hiemann, R.; Guttek, K.; Goihl, A.; Hartig, R.; Conrad, K.; Feist, E.; Sack, U.; Schierack, P., Cytometry Part A 2013, 83, 1017-1026.
Due to its advantages of being a direct comparison method, quantitative NMR spectroscopy (qNMR) becomes more and more popular in industry. While conventional high-field NMR systems are often associated with high investment and operational costs, the upcoming market of permanent-magnet based benchtop NMR systems show a considerable option for a lot of applications. The mobility of these systems allows to bring them more closely to the real production environment, e.g. for at-line quality control.
In this work we present an interlaboratory comparison study investigating the qNMR performance of state-of-the-art benchtop NMR spectrometers. Therefore, BAM prepared two samples of a mixture of NMR reference standards tetramethylbenzene (TMB) and tetrachloronitrobenzene (TCNB) at concentration levels of 200 mM and 10 mM. These “ready-to-use” samples were sent to participant laboratories, which performed analysis on their benchtop NMR equipment of different vendors and fields from 43 to 80 MHz. Raw data was reported back and further investigated by using different data analysis methods at BAM.
After this very first qNMR comparison study of benchtop NMR spectrometers show promising results, following studies are planned to cover more parts of the qNMR process, e.g. sample preparation and weighing, but also data analysis, as commonly done in similar studies for high-field NMR spectroscopy in industry and metrology.
The importance of plasmonic heating for the plasmondriven photodimerization of 4-nitrothiophenol
(2019)
Metal nanoparticles form potent nanoreactors, driven by the optical generation of energetic electrons and nanoscale heat. The relative influence of these two factors on nanoscale chemistry is strongly debated. This article discusses the temperature dependence of the dimerization of 4-nitrothiophenol (4-NTP) into 4,4′-dimercaptoazobenzene (DMAB) adsorbed on gold nanoflowers by Surface-Enhanced Raman Scattering (SERS). Raman thermometry shows a significant optical heating of the particles. The ratio of the Stokes and the anti-Stokes Raman signal moreover demonstrates that the molecular temperature during the reaction rises beyond the average crystal lattice temperature of the plasmonic particles. The product bands have an even higher temperature than reactant bands, which suggests that the reaction proceeds preferentially at thermal hot spots. In addition, kinetic measurements of the reaction during external heating of the reaction environment yield a considerable rise of the reaction rate with temperature. Despite this significant heating effects, a comparison of SERS spectra recorded after heating the sample by an external heater to spectra recorded after prolonged illumination shows that the reaction is strictly photo-driven. While in both cases the temperature increase is comparable, the dimerization occurs only in the presence of light. Intensity dependent measurements at fixed temperatures confirm this finding.
There is a need within the NMR community to progress forward in exploring new facets in which we can use analytical techniques to advance our understanding of various systems. One aspect the NMR community hasn’t fully encompassed is the validation process, which also involves setting reference standards, establishing a common language that directly relates to NMR, communication relating to validation, and much more.
This workshopcontribution starts with an overview on international metrology for qNMR spectroscopy. Since NMR is completely described by mathematical equations, the measurement unceartainty can directly be dreived from formula. Examples are presented. These are differentiated between type A and B evaluations. Finally the Expanded Unceartainty is defined. Since the user needs a risk-based unceartainty assessment, different "leagues" for routine, advanced, and high level needs are proposed to make clear, that no all sources of uncertainty have to be taken in considerention at practical levels.
Accelerating chemical process development and manufacturing along with quick adaption to changing customer needs means consequent transformation of former batch to continuous (modular) manufacturing processes. These are justified by an improved process control through smaller volumes, better heat transfer, and faster dynamics of the examined reaction systems.
As an example, for such modular process units we present the design and validation of an integrated nuclear magnetic resonance (NMR) micro mixer tailor‐made for a desired chemical reaction based on computational modelling. The micro mixer represents an integrated modular production unit as an example for the most important class of continuous reactors. The quantitative online NMR sensor represents a smart process analytical field device providing rapid and non‐invasive chemical composition information without need for calibration. We describe the custom design through computational fluid dynamics (CFD) for the demands of the NMR sensor as well as for the given reaction conditions. The system was validated with an esterification reaction as an example for a chemical reaction process.
Systems utilizing such an online NMR analyser benefits through short development and set‐up times based on “modular” spectral models. Such models can simply be built upon pure component NMR spectra within minutes to a few hours (i.e., assignment of the NMR signals to the components) instead of tedious DoE calibrations runs. We present a range of approaches for the automated spectra analysis moving from statistical approach, (i.e., Partial Least Squares Regression) to physically motivated spectral models (i.e., Indirect Hard Modelling and Quantum Mechanical calculations). The approach was validated for typical industrial reactions, such as hydrogenations or lithiations.
This work wants to show the benefit of NMR spectroscopy as online analytical technique in industrial applications for improving process understanding and efficiency. Especially development and set‐up times based on “modular” data analysis models will enable new production concepts, which are currently discussed with respect to digitization of process industry.
PANIC is the ideal forum for such discussions in the application of NMR spectroscopy and its data analysis to the everyday problems in process industry.
DNA and locked nucleic acid (LNA) were characterized as single strands, as well as double stranded DNA-DNA duplexes and DNA-LNA hybrids using tandem mass spectrometry with collision-induced dissociation. Additionally, ion mobility spectrometry was carried out on selected species. Oligonucleotide duplexes of different sequences – bearing mismatch positions and abasic sites of complementary DNA 15-mers – were investigated to unravel general trends in their stability in the gas phase. Single stranded LNA oligonucleotides were also investigated with respect to their gas phase behavior and fragmentation upon collision-induced dissociation. In contrast to the collision-induced dissociation of DNA, almost no base loss was observed for LNAs. Here, backbone cleavages were the dominant dissociation pathways. This finding was further underlined by the need for higher activation energies. Base losses from the LNA strand were also absent in fragmentation experiments of the investigated DNA-LNA hybrid duplexes. While DNA-DNA duplexes dissociated easily into single stranded fragments, the high stability of DNA-LNA hybrids resulted in predominant fragmentation of the DNA part rather than the LNA, while base losses were only observed from the DNA single strand of the hybrid.
Metastasis is the main cause of death from colorectal cancer (CRC). About 20% of stage II CRC patients develop metastasis during the course of disease. We performed metabolic profiling of plasma samples from non-metastasized and metachronously metastasized stage II CRC patients to assess the potential of plasma metabolites to serve as biomarkers for stratification of stage II CRC patients according to metastasis risk. We compared the metabolic profiles of plasma samples prospectively obtained prior to metastasis formation from non-metastasized vs. metachronously metastasized stage II CRC patients of the German population-based case–control multicenter DACHS study retrospectively. Plasma samples were analyzed from stage II CRC patients for whom follow-up data including the information on metachronous metastasis were available. To identify metabolites distinguishing non-metastasized from metachronously metastasized stage II CRC patients robust supervised classifications using decision trees and support vector machines were performed and verified by 10-fold cross-validation, by nested cross-validation and by traditional validation using training and test sets. We found that metabolic profiles distinguish non-metastasized from metachronously metastasized stage II CRC patients. Classification models from decision trees and support vector machines with 10-fold cross-validation gave average accuracy of 0.75 (sensitivity 0.79, specificity 0.7) and 0.82 (sensitivity 0.85, specificity 0.77), respectively, correctly predicting metachronous metastasis in stage II CRC patients. Taken together, plasma metabolic profiles distinguished non-metastasized and metachronously metastasized stage II CRC patients. The classification models consisting of few metabolites stratify non-invasively stage II CRC patients according to their risk for metachronous metastasis.
DNA is effectively damaged by radiation, which can on the one hand lead to cancer and is on the other hand directly exploited in the treatment of tumor tissue. DNA strand breaks are already induced by photons having an energy below the ionization energy of DNA. At high photon energies, most of the DNA strand breaks are induced by low-energy secondary electrons. In the present study we quantified photon and electron induced DNA strand breaks in four different 12mer oligonucleotides. They are irradiated directly with 8.44 eV vacuum ultraviolet (VUV) photons and 8.8 eV low energy electrons (LEE). By using Si instead of VUV transparent CaF2 as a substrate the VUV exposure leads to an additional release of LEEs, which have a maximum energy of 3.6 eV and can significantly enhance strand break cross sections. Atomic force microscopy is used to visualize strand breaks on DNA origami platforms and to determine absolute values for the strand break cross sections. Upon irradiation with 8.44 eV photons all the investigated sequences show very similar strand break cross sections in the range of 1.7 - 2.3 x 10-16 cm2. The strand break cross sections for LEE irradiation at 8.8 eV are one to two orders of magnitude larger than the ones for VUV photons, and a slight sequence dependence is observed. The sequence dependence is even more pronounced for LEEs with energies < 3.6 eV. The present results help to assess DNA damage by photons and electrons close to the ionization threshold.
Radiation therapy is a basic part of cancer treatment. To increase the DNA damage in carcinogenic cells and preserve healthy tissue at the same time, radiosensitizing molecules such as halogenated nucleobase analogs can be incorporated into the DNA during the cell reproduction cycle. In the present study 8.44 eV photon irradiation induced single strand breaks (SSB) in DNA sequences modified with the radiosensitizer 5-bromouracil (5BrU) and 8-bromoadenine (8BrA) are investigated. 5BrU was incorporated in the 13mer oligonucleotide flanked by different nucleobases. It was demonstrated that the highest SSB cross sections were reached, when cytosine and thymine were adjacent to 5BrU, whereas guanine as a neighboring nucleobase decreases the activity of 5BrU indicating that competing reaction mechanisms are active. This was further investigated with respect to the distance of guanine to 5BrU separated by an increasing number of adenine nucleotides. It was observed that the SSB cross sections were decreasing with an increasing number of adenine spacers between guanine and 5BrU until the SSB cross sections almost reached the level of a non-modified DNA sequence, which demonstrates the high sequence dependence of the sensitizing effect of 5BrU. 8BrA was incorporated in a 13mer oligonucleotide as well and the strand breaks were quantified upon 8.44 eV photon irradiation in direct comparison to a non-modified DNA sequence of the same composition. No clear enhancement of the SSB yield of the modified in comparison to the non-modified DNA sequence could be observed. Additionally, secondary electrons with a maximum energy of 3.6 eV were generated when using Si as a substrate giving rise to further DNA damage. A clear enhancement in the SSB yield can be ascertained, but to the same degree for both the non-modified DNA sequence and the DNA sequence modified with 8BrA.
Raman microspectra combine information on chemical composition of plant tissues with spatial information. The contributions from the building blocks of the cell walls in the Raman spectra of plant tissues can vary in the microscopic sub-structures of the tissue. Here, we discuss the analysis of 55 Raman maps of root, stem, and leaf tissues of Cucumis sativus, using different spectral contributions from cellulose and lignin in both univariate and multivariate imaging methods. Imaging based on hierarchical cluster analysis (HCA) and principal component analysis (PCA) indicates different substructures in the xylem cell walls of the different tissues. Using specific signals from the cell wall spectra, analysis of the whole set of different tissue sections based on the Raman images reveals differences in xylem tissue morphology. Due to the specifics of excitation of the Raman spectra in the visible wavelength range (532 nm), which is, e.g., in resonance with carotenoid species, effects of photobleaching and the possibility of exploiting depletion difference spectra for molecular characterization in Raman imaging of plants are discussed. The reported results provide both, specific information on the molecular composition of cucumber tissue Raman spectra, and general directions for future imaging studies in plant tissues.
The departure from the current automation landscape to next generation automation concepts for the process industry has already begun. Smart functions of sensors simplify their use and enable plug-and-play integration, even though they may appear to be more complex at first sight. Monitoring specific information (i.e., “chemical” such as physico-chemical properties, chemical reactions, etc.) is the key to “chemical” process control.
The talk introduces a smart online NMR sensor module provided in an explosion proof housing as example. This sensor was developed for an intensified industrial process (pharmaceutical lithiation reaction step) funded by the EU’s Horizon 2020 research and innovation programme (www.consens-spire.eu). Due to NMR spectroscopy as an “absolute analytical comparison method”, independent of the matrix, it runs with extremely short set-up times in combination with “modular” spectral models. Such models can simply be built upon pure component NMR spectra within a few hours (i.e., assignment of the NMR signals to the components) instead of tedious calibrations runs.
The talk also generally covers current aspects of high-field and low-field online NMR spectroscopy for reaction monitoring and process control.
We present a versatile and simple method using electrochemistry for the exclusive functionalization of the edge of a graphene monolayer with metal nanoparticles or polymeric amino groups. The attachment of metal nanoparticles allows us to exploit surface-enhanced Raman scattering to characterize the chemistry of both the pristine and the functionalized graphene edge. For the pristine patterned graphene edge, we observe the typical edge-related modes, while for the functionalized graphene edge we identify the chemical structure of the functional layer by vibrational fingerprinting. The ability to obtain single selectively functionalized graphene edges routinely on an insulating substrate opens an avenue for exploring the effect of edge chemistry on graphene properties systematically.
The fast and accurate detection of disease-related biomarkers and potentially harmful analytes in different matrices is one of the main challenges in the life sciences. In order to achieve high signal-to-background ratios with frequently used photoluminescence techniques, luminescent reporters are required that are either excitable in the first diagnostic window or reveal luminescence lifetimes exceeding that of autofluorescent matrix components. Here, we demonstrate a reporter concept relying on broad band emissive ternary quantum dots (QDs) with luminescence lifetimes of a few hundred nanoseconds utilized for prolongating the lifetimes of organic or inorganic emitters with lifetimes in the order of a very few 10 ns or less through fluorescence resonant energy transfer. Using spectrally resolved and time-resolved measurements of the system optical response we demonstrate the potential of lifetime multiplexing with such systems exemplarily for AgInS2/ZnS and CdSe/ZnS QDs.
There is an increasing interest in bridging the gap between the photoluminescence (PL) properties of nanomaterials like semiconductor nanocrystals (QDs) commonly assessed in ensemble studies and the PL features of single QDs for life sciences applications such as bioimaging studies or use in microfluidic assays. The fluorescence quantum yield (ΦF) is a key performance parameter for all molecular and nanoscale emitters, increasingly employed in nanoscience, nanotechnology, and medical diagnostics.
ΦF determines not only the signal size together with the reporter´s molar extinction coefficient, yet it is particularly relevant for nanocrystals like QDs with coordinatively bound surface ligands and size- and surface chemistry-dependent PL characteristics.
The importance of ΦF measurements at ultralow concentration encouraged us to explore the potential of fluorescence correlation spectroscopy (FCS) for the relative determination of ΦF of ligand-stabilized CdTe nanocrystals in comparison to molecular dyes with closely matching spectral properties and known ΦF.
We describe a FCS-based method for the relative determination of ΦF of dispersed QDs at ultralow concentrations, and procedures to overcome QD-inherent challenges like complex and power-dependent blinking behavior as well as ligand- and QD-specific aggregation. We could demonstrate the potential of this approach by comparison with steady state ensemble measurements.
The formation of transformation products (TPs) from contaminants and residues is becoming an increasing focus of scientific community. All organic compounds can form different TPs, thus demonstrating the complexity and interdisciplinarity of this topic. The properties of TPs could stand in relation to the unchanged substance or be more harmful and persistent. To get important information about the generated TPs, methods are needed to simulate natural and manmade transformation processes. Current tools are based on metabolism studies, photochemical methods, electrochemical methods, and Fenton's reagent. Finally, most transformation processes are based on redox reactions. This review aims to compare these methods for structurally different compounds. The groups of pesticides, pharmaceuticals, brominated flame retardants, and mycotoxins were selected as important residues/contaminants relating to their worldwide occurrence and impact to health, food, and environmental safety issues. Thus, there is an increasing need for investigation of transformation processes and identification of TPs by fast and reliable methods.
Lead isotope amount ratios are commonly used in diverse fields such as archaeometry, geochemistry and forensic science. Currently, five reference materials with certified lead isotope amount ratios are available, namely NIST SRM 981, 982 and 983, GBW-04442 and NMIJ 3681-a. Only NIST SRM 981 and NMIJ 3681-a have approximately natural isotopic compositions, and NIST SRM 981 is predominantly used for correcting mass discrimination/mass fractionation in the applied mass spectrometric procedures. Consequently, there is no other certified reference material available to be used for validation and/or quality control of the analytical procedures applied to lead isotope amount ratio measurements. To fill this gap, two new reference materials have been produced and certified for their lead isotope amount ratios. For both certified reference materials, complete uncertainty budgets have been calculated and SI traceability has been established. This provides the users with independent means for validating and verifying their analytical procedures and for conducting quality control measures. ERM-EB400 is a bronze material with a nominal lead mass fraction of 45 mg kg-1 and certified lead isotope amount ratios of n(206Pb)/n(204Pb) = 18.072(17) mol mol-1, n(207Pb)/n(204Pb) = 15.578(18) mol mol-1 and n(208Pb)/n(204Pb) = 38.075(46) mol mol-1 with the associated expanded uncertainties (k = 2) given in brackets. ERM-AE142 is a high-purity solution of lead in 2% nitric acid with a nominal mass fraction of 100 mg kg-1 and certified Pb isotope amount ratios of n(206Pb)/n(204Pb) = 21.114(17) mol mol-1, n(207Pb)/n(204Pb) = 15.944(17) mol mol-1 and n(208Pb)/n(204Pb) = 39.850(44) mol mol-1 with the associated expanded uncertainties (k = 2) given in brackets. Both materials are specifically designed to fall within the natural lead isotopic variation and to assist users with the validation and verification of their analytical procedures. Note that while one of these reference materials requires the chemical separation of Pb from its matrix (ERM-EB400), the other does not (ERM-AE142). As additional information, δ208/206PbNIST SRM981 values are provided for both materials. For ERM-AE142, a delta value of δ208/206PbNIST SRM981 = -28.21(30) ‰ was obtained, and for ERM-EB400, a delta value of δ208/206PbNIST SRM981 = -129.47(38) ‰ was obtained, with the associated expanded uncertainties (k = 2) given in brackets.
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.
Complementarity of molecular and elemental mass spectrometric imaging of Gadovist™ in mouse tissues
(2019)
Drug biodistribution analyses can be considered a key issue in pharmaceutical discovery and development. Here, mass spectrometric imaging can be employed as a powerful tool to investigate distributions of drug compounds in biologically and medically relevant tissue sections. Both matrix-assisted laser desorption ionization–mass spectrometric imaging as molecular method and laser ablation inductively coupled plasma–mass spectrometric imaging as elemental detection method were applied to determine drug distributions in tissue thin sections. Several mouse organs including the heart, kidney, liver, and brain were analyzed with regard to distribution of Gadovist™, a gadolinium-based contrast agent already approved for clinical investigation. This work demonstrated the successful detection and localization of Gadovist™ in several organs. Furthermore, the results gave evidence that gadolinium-based contrast agents in general can be well analyzed by mass spectrometric imaging methods. In conclusion, the combined application of molecular and elemental mass spectrometry could complement each other and thus confirm analytical results or provide additional information.
Correlating the photoluminescence (PL) properties of nanomaterials like semiconductor nanocrystals (QDs) and upconversion nanocrystals (UCNPs) assessed in ensemble studies and at the single particle level is increasingly relevant for applications of these nanomaterials in the life sciences like bioimaging studies or their use as reporters in microfluidic assays. Here we present a comparison of the spectroscopic properties of ensembles and single emitters for QDs like II/VI QDs and cadmium-free AIS/ZnS QDs as well as different UCNPs. The overall goal of this study was to derive particle architectures well suited for spectroscopic and microscopic applications.
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.
Due to its advantages of being a direct comparison method, quantitative NMR spectroscopy (qNMR) becomes more and more popular in industry. While conventional high-field NMR systems are often associated with high investment and operational costs, the upcoming market of permanent-magnet based benchtop NMR systems show a considerable option for a lot of applications. The mobility of these systems allows to bring them more closely to the real production environment, e.g. for at-line quality control.
In this work we present an interlaboratory comparison study investigating the qNMR performance of state-of-the-art benchtop NMR spectrometers. Therefore, BAM prepared two samples of a mixture of NMR reference standards tetramethylbenzene (TMB) and tetrachloronitrobenzene (TCNB) at concentration levels of 200 mM and 10 mM. These “ready-to-use” samples were sent to participant laboratories, which performed analysis on their benchtop NMR equipment of different vendors and fields from 43 to 80 MHz. Raw data was reported back and further investigated by using different data analysis methods at BAM.
After this very first qNMR comparison study of benchtop NMR spectrometers show promising results, following studies are planned to cover more parts of the qNMR process, e.g. sample preparation and weighing, but also data analysis, as commonly done in similar studies for high-field NMR spectroscopy in industry and metrology.
Improvement in deep process understanding is a mandatory prerequisite for the application of modern concepts like Industrial Internet of Things (IIoT) or “Industrie 4.0”. The direct hyphenation with online methods of process analytical technology (PAT) allows profound insights into the actual reactions within chemical and pharmaceutical production steps and provides necessary information for associated advanced control strategies.
While the industrial application of online Raman spectroscopy has already been successfully demonstrated, low-field NMR spectroscopy is not yet adequately developed as a robust online method for use in process industry. The high information content combined with the low calibration effort makes NMR spectroscopy a highly promising method for modern process automation with a high flexibility due to short set-up times and novel calibration concepts. This is a major advantage compared to other analytical methods, especially regarding multi-purpose plant strategies, as well as processes suffering from fluctuating quality of raw materials.
The work presented here focusses on the heterogeneous catalyzed hydrogenation of 2-butyne-1,4-diol, as a step of the synthesis of industrially important solvent tetrahydrofuran. This reaction is proceeding via an intermediate product and suffers from competitive reaction paths. In this application, online NMR and Raman spectroscopy were combined with data from classical process sensors, e.g., pressure, temperature, and flow transducers in a highly automated setup for the development of innovative control concepts.
The transition from the current automation landscape to next generation automation concepts for the process industry has already begun. Smart functions of sensors simplify their use and enable plug-and-play integration, even though they may appear to be more complex at first sight. Monitoring specific information (i.e., “chemical” such as physico-chemical properties, chemical reactions, etc.) is the key to “chemical” process control. Here we introduce our smart online NMR sensor module provided in an explosion proof housing as example.
Due to NMR spectroscopy as an “absolute comparison method”, independent of the matrix, it runs with very short set-up times in combination with “modular” spectral models. These are based on pure component NMR spectra without the need for tedious calibrations runs. We present approaches from statistical, (i.e., Partial Least Squares Regression) to physically motivated models (i.e., Indirect Hard Modelling).
Based on concentration measurements of reagents and products by the NMR analyser a continuous production and direct loop process control were successfully realized for several validation runs in a modular industrial pilot plant and compared to conventional analytical methods (HPLC, near infrared spectroscopy). The NMR analyser was developed for an intensified industrial process funded by the EU’s Horizon 2020 research and innovation programme (“Integrated CONtrol and SENsing”, www.consens-spire.eu).
Chemical companies must find new paths to successfully survive in a changing environment. The potential of digital technologies belongs to these. Flexible and modular chemical plants can produce various high-quality products using multi-purpose equipment with short down-times between campaigns and reduce time to market for new products. Intensified continuous production plants allow for difficult to produce compounds.
Therefore, fully automated “chemical” process control along with real-time quality control are prerequisites to such concepts and thus should be based on “chemical” information. The advances of a fully automated NMR sensor were exploited, using a given pharmaceutical lithiation reaction as an example process within a modular pilot plant. A commercially available benchtop NMR spectrometer was integrated to the full requirements of an automated chemical production environment such as , e.g., explosion safety, field communication, and robust evaluation of sensor data. It was thereof used for direct loop advanced process control and real-time optimization of the process. NMR appeared as preeminent online analytical tool and allowed using a modular data analysis tool, which even served as reliable reference method for further PAT applications.
In future, such fully integrated and intelligently interconnecting “smart” systems and processes can speed up the high-quality production of specialty chemicals and pharmaceuticals.
Chemical companies must find new paths to successfully survive in a changing environment. The potential of digital technologies belongs to these. Flexible and modular chemical plants can produce various high-quality products using multi-purpose equipment with short down-times between campaigns and reduce time to market for new products. Intensified continuous production plants allow for difficult to produce compounds.
Therefore, fully automated “chemical” process control along with real-time quality control are prerequisites to such concepts and thus should be based on “chemical” information. The advances of a fully automated NMR sensor were exploited, using a given pharmaceutical lithiation reaction as an example process within a modular pilot plant. A commercially available benchtop NMR spectrometer was integrated to the full requirements of an automated chemical production environment such as , e.g., explosion safety, field communication, and robust evaluation of sensor data. It was thereof used for direct loop advanced process control and real-time optimization of the process. NMR appeared as preeminent online analytical tool and allowed using a modular data analysis tool, which even served as reliable reference method for further PAT applications.
In future, such fully integrated and intelligently interconnecting “smart” systems and processes can speed up the high-quality production of specialty chemicals and pharmaceuticals.
Relative and Absolute Methods for Measuring Photoluminescence Quantum Yields of UV/vis/NIR Emitters
(2019)
One of the key spectroscopic performance parameters of molecular and particulate emitters is the photoluminescence quantum yield (PL QY) that provides a direct measure for the number of emitted per absorbed photons. This triggered the interest in methods suitable for measuring this property for emitters in various environments in the UV/vis/NIR and above 1000 nm as well as on the ensemble and single emitter level. Moreover, for nonlinear emitters like lanthanide-based upconversion nanocrystals methods including instrumentation for power density-dependent PL QY studies are required.
An overview of the research activities in Division Biophotonics of BAM is given and suitable relative and absolute methods for the deter-mination of PL QY of organic dyes and different types of application-relevant nanomaterials in dispersion and in the solid state are presen-ted. This covers also the design and calibration of integrating sphere setups, achievable uncertainties, and candidates for PL QY reference materials.
Chemical companies must find new paths to successfully survive in a changing environment. The potential of digital technologies belongs to these. Flexible and modular chemical plants can produce various high-quality products using multi-purpose equipment with short down-times between campaigns and reduce time to market for new products. Intensified continuous production plants allow for difficult to produce compounds.
Therefore, fully automated “chemical” process control along with real-time quality control are prerequisites to such concepts and thus should be based on “chemical” information. The advances of a fully automated NMR sensor were exploited, using a given pharmaceutical lithiation reaction as an example process within a modular pilot plant. A commercially available benchtop NMR spectrometer was integrated to the full requirements of an automated chemical production environment such as , e.g., explosion safety, field communication, and robust evaluation of sensor data. It was thereof used for direct loop advanced process control and real-time optimization of the process. NMR appeared as preeminent online analytical tool and allowed using a modular data analysis tool, which even served as reliable reference method for further PAT applications.
In future, such fully integrated and intelligently interconnecting “smart” systems and processes can speed up the high-quality production of specialty chemicals and pharmaceuticals.
Flexible and modular chemical plants can produce various high-quality products using multi-purpose equipment with short down-times between campaigns and reduce time to market for new products. Intensified continuous production plants allow for difficult to produce compounds.
Therefore, fully automated “chemical” process control along with real-time quality control are prerequisites to such concepts and thus should be based on “chemical” information. The advances of a fully automated NMR sensor were exploited, using a given pharmaceutical lithiation reaction as an example process within a modular pilot plant. A commercially available benchtop NMR spectrometer was integrated to the full requirements of an automated chemical production environment such as , e.g., explosion safety, field communication, and robust evaluation of sensor data. It was thereof used for direct loop advanced process control and real-time optimization of the process. NMR appeared as preeminent online analytical tool and allowed using a modular data analysis tool, which even served as reliable reference method for further PAT applications.
The talk also generally covers current aspects of high-field and low-field online NMR spectroscopy for reaction monitoring and process control and gives also an overview on direct dissolution studies of API cocrystals.
Flexible and modular chemical plants can produce various high-quality products using multi-purpose equipment with short down-times between campaigns and reduce time to market for new products. Intensified continuous production plants allow for difficult to produce compounds.
Therefore, fully automated “chemical” process control along with real-time quality control are prerequisites to such concepts and thus should be based on “chemical” information. The advances of a fully automated NMR sensor were exploited, using a given pharmaceutical lithiation reaction as an example process within a modular pilot plant. A commercially available benchtop NMR spectrometer was integrated to the full requirements of an automated chemical production environment such as , e.g., explosion safety, field communication, and robust evaluation of sensor data. It was thereof used for direct loop advanced process control and real-time optimization of the process. NMR appeared as preeminent online analytical tool and allowed using a modular data analysis tool, which even served as reliable reference method for further PAT applications.
The fluorescence lifetime is a key property of fluorophores that can be utilized for microenvironment probing, analyte sensing, and multiplexing as well as barcoding applications. For the rational design of lifetime probes and barcodes, theoretical methods have been developed to enable the ab initio prediction of this parameter, which depends strongly on interactions with solvent molecules and other chemical species in the emitters' immediate environment. In this work, we investigate how a conductor-like screening model (COSMO) can account for variations in fluorescence lifetimes that are caused by such fluorophore−solvent interactions. Therefore, we calculate vibrationally broadened fluorescence spectra using the nuclear ensemble method to obtain distorted molecular geometries to sample the electronic transitions with time-dependent density functional theory (TDDFT). The influence of the solvent on fluorescence lifetimes is accounted for with COSMO. For example, for 4-hydroxythiazole fluorophore containing different heteroatoms and acidic and basic moieties in aprotic and protic solvents of varying polarity, this approach was compared to experimentally determined lifetimes in the same solvents. Our results demonstrate a good correlation between theoretically predicted and experimentally measured fluorescence lifetimes except for the polar solvents Ethanol and acetonitrile that can specifically interact with the heteroatoms and the carboxylic acid of the thiazole derivative.
A systematic study of the luminescence properties of monodisperse β-NaYF4: 20% Yb3+, 2% Er3+ upconversion nanoparticles (UCNPs) with sizes ranging from 12–43 nm is presented utilizing steady-state and time-resolved fluorometry.
Special emphasis was dedicated to the absolute quantification of size- and environment-induced quenching of upconversion luminescence (UCL) by highenergy O–H and C–H vibrations from solvent and ligand molecules at different excitation power densities (P). In this context, the still-debated Population pathways of the 4F9/2 energy level of Er3+ were examined. Our results Highlight the potential of particle size and P value for color tuning based on the pronounced near-infrared emission of 12 nm UCNPs, which outweighs the red Er3+ emission under “strongly quenched” conditions and accounts for over 50% of total UCL in water. Because current rate equation models do not include such emissions, the suitability of these models for accurately simulating all (de)population pathways of small UCNPs must be critically assessed. Furthermore, we postulate population pathways for the 4F9/2 energy level of Er3+, which correlate with the size-, environment-, and P-dependent quenching states of the higher Er3+ energy levels.