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- 1.1 Anorganische Spurenanalytik (51) (entfernen)
Per- and polyfluorinated alkyl substances (PFASs) are a substance class of over 4730 individual compounds. Several PFASs are extremely persistent, bioaccumulative and toxic. The analysis of PFASs is challenging because of their different chemical and physical properties as well as the high number of target substances. Target-based approaches (e.g., LC-MS/MS) are limited to the availability of analytical grade standards and are not suitable for the analysis of new/unknown PFASs and transformation products. Therefore, PFAS sum parameter methods become increasingly important to indicate a realistic PFAS pollution level.
PFAS sum parameters compromise the proportion of organically bound fluorine that can either be extracted (EOF) or adsorbed to activated carbon (AOF). For the instrumental analysis of such sum parameters, a fluorine selective detector is needed. High resolution-continuum source-graphite furnace molecular absorption spectrometry (HR-CS-GFMAS) is a sensitive and highly selective tool for indirect fluorine determination. The method is based on the in situ formation of diatomic gallium-mono fluoride (GaF) in a graphite furnace at a temperature of 1550°C. The molecular absorption of GaF can be detected at its most sensitive wavelength at 211.248 nm providing limits of quantification of c(F) 2.7 µg/L.
Here, we describe a fast and simple extraction method for the determination of the EOF using HR-CS-GFMAS in soil samples. Common approaches for the EOF determination use solid phase extraction (SPE). To omit the bias of this time consuming and expensive step we optimized a fast and simple SPE-free extraction method. The developed extraction method consists of a liquid-solid extraction using acidified methanol. Comparison of the method with and without an SPE clean-up step revealed a drastic underestimation of EOF concentrations using SPE. In the next step, the applicability of our method was tested for other solid matrices. In view of steadily increasing numbers of PFASs, our method will make an important contribution in assessing the pollution situation as well as support policy makers in deriving exposure limits for PFASs in the future.
Here, we describe a fast and simple extraction method for the determination of per- and polyfluorinated alkyl substances (PFASs) utilizing extractable organic fluorine (EOF) sum parameter analysis and high resolution-continuum source-graphite furnace molecular absorption spectrometry (HR-CS-GFMAS) in soil samples. After extraction and separation of inorganic and organic fluorinated compounds, organically bound fluorinated compounds were indirectly determined via the molecular absorption of gallium mono-fluoride at 211.248 nm. The implementation of the decisions of the “Stockholm Convention on persistent organic pollutants” as well as the “Protocol on Persistent Organic Pollutants of the Convention on Long-Range Transboundary Air Pollution” of the UNECE include the reduction respectively the elimination of PFASs in the environment. Currently, regulations aim to target single compounds (mostly C8-PFAS). But the PFAS group includes over 4700 substances, which are potentially persistent and toxic, thus target analytical approaches are not suitable for a holistic approach investigating the PFAS pollutant situation. Furthermore, forbidden PFASs are substituted by short-chain PFASs, thus the number of unknow substances is steadily increasing. For this reason, sum parameter approaches are more suitable to investigate and assess the pollution situation as well as derive exposure limits. Our developed analytical method was successfully applied to determine PFASs in soil samples from a polluted site. In view of steadily increasing numbers of PFAS substances, our method will make an important contribution in assessing the pollution situation as well as support policy makers in deriving exposure limits for PFAS in the future.
For the first time polyethylene (PE) frits were used to quantify sulphur in copper metal and its alloys by isotope dilution combined with LA-ICP-MS: an alternative approach for sample preparation. The properties of the PE frit meet the requirements for isotope dilution LA-ICPMS which are porous material, thermal and chemical resistance and high absorption efficiency. The breakthrough, however, as a support material, is the low sulphur blank, which is only two times of the gas flow blank (2.3-4.0 x 10⁴ cps). Additionally, the porosity of the frit was considered, as it directly affects the absorption efficiency for the sample solution, which is present in the cavities of the frit.
The absorption efficiency was studied by loading sulphur standards with varying sulphur amounts (0 - 80 µg S) onto the frits. The remaining sulphur which was not absorbed by the frit was rinsed off and was measured by ICP-MS. This indirect method shows that more than 99.5 % of the loaded sulphur was absorbed by the frit. The so prepared frits with increasing sulphur amount were measured by LA-ICP-MS showing a good linearity between 0 µg S and 40 µg S with a coefficient of determination, r2 of 0.9987 and a sensitivity of 3.4x10⁴ cps µgˉ¹ for 32S.
Three copper reference materials produced by BAM (BAM-M376a, BAM-228 and BAM-227) were selected to develop and validate the LA-ICP-IDMS procedure. The IDMS technique was applied to these samples as follows: the samples were spiked, dissolved, digested and then the digested solution was absorbed on the frits. The dried frit samples were then analyzed by LA-ICP-IDMS and it could be demonstrated that the sample solution dispersed on the frits did not influence the 32S/34S ratio significantly even though the sulphur intensities were fluctuating along the scan lines. Relative standard deviations of the isotope ratios were below 5 % in average between 3 lines (except for the pure spike solution and procedure blank). The measurement results were validated by comparing them with the results obtained by conventional ICP-IDMS. Plotting the mass fraction of sulphur in copper obtained by LA-ICP-IDMS versus those obtained by ICP-IDMS yields a linear curve with a correlation coefficient of 0.9999 showing a strong agreement between both techniques.
The metrological traceability to the SI for the mass fraction of sulphur in copper is established by an unbroken chain of comparisons, each accompanied by an uncertainty budget. Thus, the measurement results are considered reliable, acceptable and comparable within the stated measurement uncertainty. The metrological traceability chain from the kg down to the final mass fraction in the samples obtained by LA-ICP-IDMS is illustrated in this presentation.
Iron isotopes are used in a variety of fields from e.g., geologic question to medical applications. Measurements of iron isotopes are usually performed as delta measurements to an artificial based delta zero standard. In the case of Fe isotopes is that delta zero standard IRMM-014, a pure Fe metal. Unfortunately, that conventional delta zero reference material defining the 56/54Fe scale is out of stock and therefore unavailable. To overcome that situation and fulfill the need for laboratories that measure Fe isotope on a regular basis we will provide a set of solutions with IRMM-014 and a second anchor point for Fe isotope ratio measurements that is based on a pure Fe metal. This new second anchor point, a high purity Fe from BAM, will be calibrated against IRMM-014 and can be used as bracketing standard or as reference value for stable Fe isotope measurements.
We are in the good situation that BAM ordered a large stock of IRMM-014 several years ago. That stock of IRMM-014 Fe cubes and IRMM-014 Fe wires will be dissolved in 6M HCl in a large quantity. The new anchor point, the high purity Fe metal, that is commercially available at BAM, is a pure Fe metal with only trace amounts of impurities. The high purity BAM material will also be dissolved in 6M HCl in large quantity. Several aliquots of both solutions will be measured on the Neptune Plus MC-ICP-MS to define this second anchor point with a low uncertainty. Further will we send several aliquots of both solutions to different laboratories to also measure this second anchor point of high purity Fe on the 56/54Fe scale.
We will report the values of that study on BAM high purity Fe and will provide a guide for scale conversion to the IRMM-014 scale and for uncertainty calculation to use that new anchor point instead of the exhausted IRMM-014.
HR-CS-GFMAS turned out to be a sensitive, fast and highly selective tool for fluorine determination. The method is based on the in situ formation of diatomic gallium-mono fluoride (GaF) at a temperature of 1550°C. GaF can be detected at 211.248 nm providing limits of quantificationin the low μg/L range. However, several species specific effects where observed when analyzing PFASs.
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.
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.
Nearly all disease processes are associated with variations of components of the extracellular matrix (ECM) that are typically observed during the development of inflammation. This concerns for example proteoglycans and their associated glycosaminoglycans (GAG), which have been shown to bind to cationic metal imaging probes due to their strong complexing activity. The complexing activity largely depends on the degree of GAG sulfation and/or carboxylation as well as on the GAG isomericity. In this central project, we investigate GAG structures from inflammatory disorders (namely cardiovascular diseases, inflammatory intestinal diseases and neuroinflammation) provided by researchers of the Collaborative Research Center at the molecular disaccharidic level using chromatographic and mass spectrometric methods. In parallel, the spatial localization and quantification of metal-based imaging probes are evaluated by LA-ICP-MS imaging.
ICP-ToF (time of flight) MS enables the analysis of the multi-element fingerprint of single cells. The single cell ICP-ToF-MS is used in the presented poster for the analysis of archaea involved in microbiologically influenced corrosion (MIC) of steel. By means of sc-ICP-ToF-MS, the possible uptake of individual elements from the respective steel is investigated - the information obtained will be used in the future to elucidate underlying mechanisms and develop possible material protection concepts. The work combines modern methods of analytical sciences with materials.
Deciphering microbiological influenced corrosion processes on steel with single cell-ICP-ToF-MS
(2022)
Microbiologically influenced corrosion (MIC) is a highly unpredictable process dictated by the environment, microorganisms, and the respective electron source. Interaction pathways between cells and the metal surface remain unclear. The development of this novel single cell-inductively coupled plasma-time of flight-mass spectrometry analytical method and a MIC-specific staining procedure facilitate the investigation of steel-MIC interactions. With this it is possible to analyze the multi-elemental fingerprint of individual cells. The detection method revealed elemental selectivity for the corrosive methanogenic archaeal strain Methanobacterium-affiliated IM1. The interface between material and environmental analysis thus receives special attention, e.g., when considering MIC on solid steel. Hence, the possible uptake of individual elements from different steel samples is investigated. Results showed the cells responded at a single-cell level to the different types of supplemented elements and displayed the abilities to interact with chromium, vanadium, titanium, cobalt, and molybdenum from solid metal surfaces. The information obtained will be used in the future to elucidate underlying mechanisms and develop possible material protection concepts, thus combining modern methods of analytical sciences with materials research.
References.
ICP-ToF (Flugzeitanalysator, engl. time of flight)-MS ermöglicht den Multielement Fingerabdruck einzelner Zellen (single cell) zu analysieren. Die single cell-ICP-ToF-MS kommt bei dem vorgestellten Poster bei der Analyse von Archaeen, die an mikrobiell beeinflusster Korrosion (engl. microbiologically influenced corrosion, MIC) von Stahl eine Rolle spielen, zum Einsatz. Mittels sc-ICP-ToF-MS wird die mögliche Aufnahme von einzelnen Elementen aus dem jeweiligen Stahl untersucht – die erhaltenen Informationen fließen zukünftig in die Aufklärung zugrunde liegender Mechanismen sowie Entwicklung möglicher Materialschutzkonzepte ein. Die Arbeiten Verknüpfen moderne Methoden der Analytical Sciences mit Materialien.
Up to now, different analytical methods for single cell analysis exist focusing on key features such as size, shape, morphology and elemental composition. The combination of the latest ICP-MS techniques - ICP-ToF-MS - together with the latest developments in the field of sample delivery - micro droplet generator (MDG) – will allow a Deep insight into the composition and size of cells.
Microbiologically influenced corrosion (MIC) is an oxidation of metals affected by the presence or activity (or both) of microorganisms e.g. Shewanella Putrefaciens in biofilms on the surface of the corroding material. As this can happen for example in the soil on iron pipes of water pipes, in oil tanks or on steel sheet piling, there is great interest in MIC research, not only from various industrial sectors, but also from the environmental aspect.
The quantification of the exact amount of sulphur is a big challenge due to a lack of SI-traceability and inconsistent results, when different methods are compared. Therefore, a reference procedure is required which allows SI-traceable values. In this work three procedures were developed for the quantification of the total sulphur amount in biodiesel by using inductively coupled plasma-isotope dilution mass spectrometry (ICP-IDMS), pure copper metals and copper alloys by ICP-IDMS and external calibration for GDMS and LA-ICP-MS at low concentration levels.
The most critical parts of the sulphur quantification were sulphur purification and pre-concentration. Sulphur-matrix separation procedures were developed to serve both sample types. For biodiesel samples the sulphur was purified and matrix separated by an anion exchange chromatographic procedure. The analytical procedure was fully validated by the use of a certified reference material, a step-by-step validation and an inter-laboratory comparison at CCQM key comparison level.
In the case of copper samples, the copper matrix was separated from sulphur by adding ammonia which forms a complex with the copper while releasing the sulphur prior to a chromatographic separation using a weak cation resin. After that the sulphur fraction was further purified by chromatographic means using first an anion ion exchange method and second a chelating resin. The method was validated by appropriate certified reference materials. The developed procedures enable sulphur measurements at the low g·g-1 level with sufficiently low measurement uncertainties (< 2 %, Urel).
The external calibration was performed to produce reliable measurement results for the routine analytical techniques GDMS and LA-ICP-MS. Matrix-matched reference materials whith exactly known amount of sulphur obtained by ICP-IDMS beforehand, were used as calibrators to quantify sulphur in copper samples. The metrological traceability to the SI for the mass fraction of sulphur is established for all presented procedures by an unbroken chain of comparisons, each accompanied by an uncertainty budget.
The introduction of fluorine in organic molecules leads to new chemical/physical properties. Especially in the field of pharmaceuticals, fluorinated organic molecules are becoming more and more popular and at present amount up to 25% of market share, with an upward trend. The main benefits of fluorinated pharmaceuticals are: (i) enhanced fat solubility; (ii) enhanced interaction of catalytic-center of enzymes with fluorine-drugs; (iii) a delayed metabolism within the human body. Highly fluorinated organic substances are also used in technical applications (e.g. coatings, fire-extinguishing agents).
Due to the broad variety of fluorinated substances and increasing production volumes numerous and up to date unknown fluorine-species are most likely to be present in the (aquatic) environment. Analytical methods to assess the degree of contamination of surface waters with organically bound fluorine are highly needed and up to now only combustion ion chromatography based method is available, which is relatively laborious.
Since a few years’ high resolution-continuum source-graphite furnace atomic absorption spectrometers (HR-CS-GFAAS) are commercially available from Analytik Jena. By means of this technique, the detection of high resolution molecular absorption spectra (MAS) is enabled. Thus, fluoride is detectable upon the addition of a modifier and the formation of a diatomic molecule (e.g. GaF). Just recently, we applied this technique for total fluorine (mainly dissolved fluoride) analysis in river water samples.
In the present work a HR-CS-GFMAS method for extractable organically bound fluorine (EOF) analysis in surface water samples was developed by us. The method is based on SPE extraction of organically bound fluorine even in the presence of high fluoride concentrations followed by HR-CS-GFMAS analysis upon elution. Due to high enrichment factors, LODs in the low ng/L range were achieved. We successfully applied our SPE HR-CS-GFMAS method to Rhine water samples and EOF in the range of about 50-300 ng/L was detectable.
Per- and polyfluorinated alkyl substances (PFASs) are a group of several thousand individual compounds. Many PFASs are extremely persistent, bioaccumulative and toxic. The analysis of PFASs is challenging because of their various chemical and physical properties as well as the high number of compounds. Target-based approaches (e.g., LC-MS/MS) are limited to the availability of analytical grade standards and are not suitable for the analysis of new/unknown PFASs and transformation products. Therefore, PFAS sum parameter methods become increasingly important to indicate realistic PFAS pollution levels.
PFAS sum parameters display the proportion of organically bound fluorine that can either be extracted (EOF) or adsorbed to activated carbon (AOF). For the instrumental analysis of such sum parameters, a fluorine selective detector is needed. High resolution-continuum source-graphite furnace molecular absorption spectrometry (HR-CS-GFMAS) is a sensitive and highly selective tool for fluorine determination. The method is based on the in situ formation of diatomic gallium-mono fluoride (GaF) in a graphite furnace at a temperature of 1550°C. The molecular absorption of GaF can be detected at its most sensitive wavelength at 211.248 nm providing limits of quantification of c(F) 2.7 µg/L.
In the present work a HR-CS-GFMAS method for EOF analysis was utilized for suspended particulate matter (SPM) analysis in German rivers in time lines from 2005–2020. Therefore, time and spatial resolved trends were investigated. In addition, SPM samples were analyzed for the Σ41PFAS using target analysis based on UHPLC-HRMS. Overall, target analysis drastically underestimated the total PFAS burden in SPM of German rivers compared to the EOF HR-CS-GFMAS analysis. Using a fluorine mass balance approach, only 0.2% to 38.6% of the EOF was explainable using the Σ41PFAS determined with target analysis. Our study highlights the need to integrate PFAS sum parameters (e.g., EOF with HR-CS-GFMAS) in PFAS risk assessment strategies.
Multiple sclerosis (MS) is the most common acquired neurological disease affecting Young adults. It leads to myelin destruction and formation of lesions in the brain and permeabilization of the blood-brain barrier (BBB).
Gadolinium based contrast agents (GBCA), used for diagnosis and monitoring by MRI, might accumulate in tissue, including brain. Using an animal model, application of linear and macrocyclic GBCA was investigated. Analysis was performed by laser ablation inductively coupled plasma (LA-ICP) MS. This method works as a bioimaging tool for sample thin sections and allows to identify regions of accumulated Gd in the samples.
In healthy and diseased mice, inflammationmediated changes in the brain were investigated by application of GBCA. The mean objective is to understand the changes in inflamed tissue and correlate alterations of the BBB by LA-ICP-MS (Imaging Mass Cytometry).
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.
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 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.
In this study, we developed a new immunoprecipitation method based on protein-coated nanodiamonds. Performing SDS-PAGE and using the SDS-PAGE buffer as an eluent showed that CER could be successfully enriched from human serum. Based on the copper determination with ICP-MS, the amount of bound CER on the nanodiamonds can be calculated. We could show the fulfilled mass balance of bound CER and CER in the supernatant after incubation with a known amount of CER. For isotope ratio analysis this method can be applied to compare ratios of the total copper content in human serum to copper ratios from CER enrichment.
The variation of isotope ratios is increasingly used to unravel natural and technical questions. With new upcoming techniques and research topics in the last two decades, such as material provenance or food authenticity to animal and human migration studies, the number of published isotope data has strongly increased. Here, isotope reference materials are indispensable to enable a reliable method validation or even SI-traceability. The fast development and broad availability of inductively coupled plasma mass spectrometry instrumentation (ICP-MS) also lead to an expansion of the classical research areas and new elements are under investigation. Owing to this large expansion of the field, the production and certification of isotope reference materials for calibration and validation is lagging behind, even for classical applications such as conventional 87Sr/86Sr isotope ratio analysis. To improve this situation, BAM organized an interlaboratory comparison (ILC) comprising of thirteen international laboratories for the characterisation of 87Sr/86Sr isotope ratios in geochemical and industrial reference materials. Six reference materials (four cements and two rocks) were provided as powder requiring extensive sample preparation prior to isotopic measurement. Additional requirements included the use of the conventional method for obtaining 87Sr/86Sr isotope ratios, also known as radiogenic 87Sr/86Sr isotope ratios, and the assessment of the measurement uncertainty. The primary goal was to evaluate potential differences in the application of multicollector thermal ionization mass spectrometry (MC-TIMS) and multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) for conventional 87Sr/86Sr isotope ratio determination, with a secondary goal to provide reference values for the 87Sr/86Sr isotope ratios in these potential new reference materials. All reported results are accompanied by an uncertainty statement and are traceable to the conventional method, which will be described in detail within this presentation. Current state-of-the-art statistical models were used to ensure the proper evaluation of the reported results and their associated measurement uncertainties within the frame of this ILC. Combined with results from appropriate homogeneity assessment, reference values for 87Sr/86Sr isotope ratios will be assigned.
The Federal Institute for Materials Research and Testing (BAM) organised an interlaboratory comparison (ILC) for the characterisation of 87Sr/86Sr isotope ratios in limestone (IAG/CGL ML-3) and Penrhyn slate (IAG OU-6) reference materials by applying the conventional method for 87Sr/86Sr isotope ratios. Samples were sent to thirteen analytical laboratories . Since both samples are powdered, rock materials, dissolution of the sample and Sr isolation via ion exchange chromatography were mandatory. This was done using acid, microwave/acid, bomb/acid digestion or borate fusion and subsequent isolation of Sr by means of commercially available ion exchange resins. In this study, we present and discuss the potential effects that differences between laboratories, and between two instrumental measurement techniques (i.e., MC-ICP-MS and MC-TIMS), may have upon the dispersion of measurement results of the 87Sr/86Sr isotope ratio in the two aforementioned reference materials. We used a statistical mixed effects model to assess the potential effects of both the laboratory and the measurement technique. Consensus values for both materials and associated standard uncertainties {(IAG/CGL ML-3 (0.708245±0.000004) mol/mol; IAG OU-6 (0.729769±0.000008) mol/mol} were estimated by fitting a linear, Gaussian mixed effects model (Pinheiro and Bates 2000) using the R function “lmer” defined in package “lme4”. The statistical results showed that there is no significant effect attributable to differences between instrumental techniques when both materials are considered together, or separately. The p-value of the test of significance of the measurement technique effect is greater than 0.54. For both materials there were statistically significant effects attributable to differences between laboratories when the measurement results for both materials were considered together and separately. This effect is less than 0.00004 in absolute value. However, for neither material did consideration or disregard for such differences induce significant changes in the estimate of the consensus value for the 87Sr/86Sr isotope ratio. Therefore, the effects attributable to differences between instrumental techniques or between laboratories can safely be disregarded when computing the best estimate for the true value of 87Sr/86Sr isotope ratio in these materials, by the community of expert laboratories represented in this study.
Thirteen laboratories participated in an international interlaboratory comparison for the determination of 87Sr/86Sr isotope ratios in four cement reference materials (RM) using the conventional method for 87Sr/86Sr isotope ratios analyses. Sample dissolution and Sr isolation via ion exchange chromatography were required since the cement samples were distributed as powders. Analytical preparation included the use of various digestion methods including mixed mineral acids, microwave/acid, bomb/acid digestion or borate fusion, followed by Sr separation using ion exchange chromatography. In this study, we evaluated whether any statistically significant differences were attributable to instrumental differences (i.e., MC-ICP-MS and MC-TIMS), or to laboratory-specific techniques (different sample preparation techniques, Sr isolation and the procedures for correcting the data outputs). To evaluate these effects, consensus values for cement RMs and associated standard uncertainties were estimated by fitting a linear, Gaussian mixed effects model using the R function “lmer” defined in package “lme4”. No statistically significant effects (SSE) attributable to instrumental differences regardless of whether the materials are considered together or separately were evident. There were SSE attributable to differences between laboratories for three cement RMs when the individual cements were considered separately. Since consideration or disregard for such differences does not induce significant changes in the estimate of the consensus values for the 87Sr/86Sr isotope ratios in cement RMs, these effects can safely be neglected when calculating the best estimates for the true values of 87Sr/86Sr isotope ratios in these RMs.
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.
In this poster for the SCIX Conference, we apply an analytical procedure based on the monitoring of the lithium isotope through the partially resolved isotope shift in the electronic transition 22P<-22S around wavelength 670.80 nm using high-resolution continuum source atomic absorption spectrometer (HR-CS-AAS) in combination with machine learning (ML) for the determination of Li Isotope ratio analysis.
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.
In the interest of exploring their potential in the field of single particle analysis, a Microdroplet Generator (MDG) was coupled to an ICP-ToF-MS. Isotopic Dilution Analysis was also incorporated for the size determination of three different Platinum nanoparticles samples (50, 63 and 70 nm). The performance of the technique was validated by comparison to traditional size characterization techniques (sp-ICP-ToF-MS, TEM), while the robustness of the technique was proven by incorporating NaCl in the samples’ matrix, up to 100 mg/L.
Imaging of elemental distributions in single cell assays as well as tissue sections can be performed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). This powerful technique offers precise spatially resolved measurements at trace and ultratrace levels and has been established as an excellent tool to answer analytical, biological and biomedical questions. To date, mass cytometry is already able to simultaneously detect up to 40 cellular targets due to conjugation of isotopically pure lanthanides to affinity binders, e.g. antibodies.
To further enhance the ability of multiparametric analysis to more than 100 analytes at once, we investigated lanthanide nanocrystals as new, highly sensitive metal tags for identification of targets in clinical cell assays and tissue samples. Multiparametric analysis will be possible by encoding the lanthanide composition of nanocrystals associated to the affinity binders. Nanocrystals showed remarkable potential for sensitive detection in MS due to high stability and signal amplification compared to e.g. polymer tags, carrying fewer metal atoms. Furthermore, the nanocrystals allow multimodal imaging due fluorescence of Eu3+ as well as contrast enhancing properties of Gd3+ in magnetic resonance imaging.
Synthesis of functionalized lanthanide nanocrystals for further bioconjugation was performed with high reproducibility and monodisperse size distribution. For proof of principle, the uptake and distribution of these nanocrystals within the monolayered cell line A549 were investigated by mapping the intensities at subcellular resolution using LA-ICP-MS. It could be shown, that the cells were efficiently labeled with the nanocrystals. Additionally, the bioconjugation of the nanocrystals to antibodies and particularly the preservation of the antibody specificity was investigated using Dot Blot experiments. All in all, the results imply high sensitivity and the possibility of multiparametric analysis by doting various lanthanides into the nanocrystals.
Imaging of elemental distributions in single cell assays as well as tissue sections can be performed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). This powerful technique offers precise spatially resolved measurements at the trace and ultratrace level and has been established as an excellent tool to answer analytical, biological and biomedical questions. To date, imaging mass cytometry is already able to simultaneously detect up to 40 cellular targets due to conjugation of isotopically pure lanthanides to affinity binders, e.g. antibodies.
To further enhance the ability of multiparametric analysis to more than 100 analytes at once, we investigated lanthanide nanocrystals as new, highly sensitive metal tags for identification of targets in clinical cell assays and tissue samples. Multiparametric analysis will be possible by encoding the lanthanide composition of nanocrystals associated to the affinity binders. Nanocrystals showed remarkable potential for sensitive detection in MS due to high stability and signal amplification compared to e.g. polymer tags, carrying fewer metal atoms.
Synthesis of functionalized lanthanide nanocrystals for further bioconjugation was performed with high reproducibility and monodisperse size distribution. For proof of principle, the uptake and distribution of these nanocrystals within the monolayered cell line A549 were investigated by mapping the intensities at subcellular resolution using LA-ICP-MS. It could be shown, that the cells were efficiently labeled with the nanocrystals and mostly accumulate near the nucleus. Additionally, the bioconjugation of the nanocrystals to antibodies and particularly the preservation of the antibody specificity was investigated using Dot Blot experiments. All in all, the results imply high sensitivity and the possibility of multiparametric analysis by doting various lanthanides into the nanocrystals.
Imaging of elemental distributions in single cell assays as well as tissue sections can be performed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). This powerful technique offers precise spatially resolved measurements at trace and ultratrace levels and has been established as an excellent tool to answer analytical, biological and biomedical questions. To date, mass cytometry is already able to simultaneously detect up to 40 cellular targets due to conjugation of isotopically pure lanthanides to affinity binders, e.g. antibodies.
To further enhance the ability of multiparametric analysis to more than 100 analytes at once, we investigated lanthanide nanocrystals as new, highly sensitive metal tags for identification of targets in clinical cell assays and tissue samples. Multiparametric analysis will be possible by encoding the lanthanide composition of nanocrystals associated to the affinity binders. Nanocrystals showed remarkable potential for sensitive detection in MS due to high stability and signal amplification compared to e.g. polymer tags, carrying fewer metal atoms. Furthermore, the nanocrystals allow multimodal imaging due fluorescence of Eu3+ as well as contrast enhancing properties of Gd3+ in magnetic resonance imaging.
Synthesis of functionalized lanthanide nanocrystals for further bioconjugation was performed with high reproducibility and monodisperse size distribution. For proof of principle, the uptake and distribution of these nanocrystals within the monolayered cell line A549 were investigated by mapping the intensities at subcellular resolution using LA-ICP-MS. It could be shown, that the cells were efficiently labeled with the nanocrystals. Additionally, the bioconjugation of the nanocrystals to antibodies and particularly the preservation of the antibody specificity was investigated using Dot Blot experiments. All in all, the results imply high sensitivity and the possibility of multiparametric analysis by doting various lanthanides into the nanocrystals.
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is gaining importance for bioimaging cytometry to answer analytical, biological and biomedical questions. High sensitivity and spatial resolution make it an excellent tool for imaging of metal and heteroelement distribution in single cells. Comparable to CyTOF imaging mass cytometry, metal coded antibodies can be used for multiparametric analysis as well as quantification.
In this project, nanocrystals are investigated as new highly sensitive metal tags for identification and quantification of biomarkers, like Alzheimer’s or breast cancer, in clinical cell assays and tissue samples. Of high significance is the simultaneous analysis of several biomarkers at once, which is possible by special coding of lanthanide tags on the biomarker associated antibody. Nanocrystals show potential for sensitive measurement in MS due to high stability and signal amplification compared to tags with fewer metal atoms. For proof of principle, synthesis and characterization of lanthanide doped nanocrystals was performed by a nanoPET pharma GmbH with great reproducibility and homogenous size. In A549 cell cultures, the uptake and distribution of these nanocrystals within the monolayered cells was investigated by LA-ICP-MS measurements using subcellular resolution. The nanocrystals showed high sensitivity and the possibility of multiparametric analysis by doting different lanthanides. Additionally, stability of the bioconjugation of the nanocrystals and target antibodies was investigated using Dot Blot experiments and LA-ICP-MS.
In many scientific fields, isotopic analysis can offer valuable information. Up to date, typically bulk analysis is aimed at measuring the isotopic composition of the entire elemental content of the sample. However, the analyte element is usually present under the form of different species. Thus, separating species of interest from one another and from matrix components prior to isotope ratio measurements can provide species-specific isotopic information, which could be used for tracing the origin of environmental pollutants and elucidation of (environmental) speciation. Using on-line hyphenations of separation techniques with multicollector-ICP-MS (MC-ICP-MS) can save time and effort and enables the analysis of different species during a single measurement. Whereas some works hyphenating GC and IC with MC-ICP-MS have already been reported, LC and CE hyphenations are still inadequately represented based on the capabilities of these separation techniques.
In this work, we developed an on-line hyphenation of CE with multicollector-ICP-MS (CE/MC-ICP-MS) for isotopic analysis of sulfur species using a multiple-injection approach for instrumental mass bias correction by standard-sample bracketing. With this method, the isotopic composition of sulfur in sulfate originating from river water could be analyzed without sample preparation. The results were compared to data from off-line analysis of the same samples for validation. The repeatability of the results of the on-line measurements was promising regarding the differentiation of the river systems by the isotopic signature of river water sulfate. The great potential of this method is based on the versatility of the applied separation technique, not only in the environmental field but also for, e.g., biomolecules because sulfur is the only covalently bound constituent of proteins that can be analyzed by MC-ICP-MS.
Optimization of protein quantification via isotope dilution ICP-MS of a standard reference protein
(2019)
Quantitative proteomics are nowadays one of the key tasks in life sciences. A multitude of methods for protein quantification are established and more techniques are developed each year, but there still is a lack of well characterized and quantified protein standards. We aim to develop an ICP-MS based method to quantify pure proteins reliably and traceable to SI. Here, we employ isotope Dilution analysis for the quantification of proteins of known stoichiometry via their sulfur content.
Abstract: Since it is unknown for many applications, which PFASs are used and how they enter the environment, target analysis-based methods reach their limits. The two most frequently used sum parameters are the adsorbable organically bound fluorine (AOF) and the extractable organically bound fluorine (EOF). Both can be quantified using either combustion ion chromatography (CIC) or high resolution-continuum source-graphite furnace molecular absorption spectrometry (HR-CS-GFMAS). Here we provide an insight on the advantageous and disadvantageous of both sum parameters and both detection methods. Our study is based on the analysis of surface water samples. Next to total fluorine (TF) analysis, AOF and EOF were determined as well as CIC and HR-CS-GFMAS are compared and results are comparatively discussed. Fluorine mass balancing revealed that, the AOF/TF proportion was higher than the EOF/TF proportion. The AOF made up 0.14–0.81% of TF and the EOF 0.04–0.28% of TF. Although, organically bound fluorine represents only a small portion of TF, PFASs are of worldwide concern, because of their extreme persistence and their bioaccumulation potential. The EOF-HR-CS-GFMAS method turned out to be more precise and sensitive than the AOF-CIC method and is a promising tool for future monitoring studies/routine analysis of PFASs in the environment.
Organophosphate (OP) esters (OPEs) are widely used as flame retardants (FRs) and can for that purpose be found in textiles, furnitures, electronics and more. They can also be used as plasticizers or lubricants. OPEs have been found in air, water and sediment as environmental pollutants and are associated with potential health risks like cancer.
In this study, a method for the phosphorus sum parameter analysis using HR-CS-GFMAS was optimized for environmental (water) samples. For this purpose, three FR substances (TPP, VPA, TDCPP) were used.
Silver nanoparticles (AgNPs), have a high scientific and commercial impact due to their important antibacterial properties. However, there are serious concerns about their toxicological adverse effects as a consequence of their broad range of applications. Particularly, the impact of AgNPs on cells is not very well understood yet and there is a current demand to develop analytical methodologies providing information about the interaction and distribution of AgNPs at a single cell level. In this research, mass cytometry was used to introduce a new quantitative approach to study the uptake of AgNPs by individual THP-1 macrophages as a cell model system. Here, we show that this methodology provides not only multi-variate phenotypic information of individual cells but enables the quantitative analysis of AgNPs associated to cells in a single measurement by performing an external calibration using AgNPs suspension. Using differentiated THP-1 cells, we monitored and quantified the uptake of 50 nm AgNPs in a time and dose-dependent manner by mass cytometry. 7 to 120 AgNPs per cell (2 to 89 fg Ag/cell) were determined after exposure of differentiated THP-1 cells to low AgNPs concentrations of 0.1 and 1.0 mg L-1, at time points of 4 and 24 h. The results were validated by mass cytometric analysis of digested cells working as a conventional inductively coupled plasma mass spectrometry, ICP-MS. This study demonstrates the power of single cell analysis by mass cytometry even for low doses experiments as a new analytical tool for hitherto unaddressed questions in nanotoxicology.
Silver nanoparticles (AgNPs), have a high scientific and commercial impact due to their important antibacterial properties. However, there are serious concerns about their toxicological adverse effects as a consequence of their broad range of applications. Particularly, the impact of AgNPs on cells is not very well understood yet and there is a current demand to develop analytical methodologies providing information about the interaction and distribution of AgNPs at a single cell level. In this research, mass cytometry was used to introduce a new quantitative approach to study the uptake of AgNPs by individual THP-1 macrophages as a cell model system. Here, we show that this methodology provides not only multi-variate phenotypic information of individual cells but enables the quantitative analysis of AgNPs associated to cells in a single measurement by performing an external calibration using AgNPs suspension. Using differentiated THP-1 cells, we monitored and quantified the uptake of 50 nm AgNPs in a time and dose-dependent manner by mass cytometry. 7 to 120 AgNPs per cell (2 to 89 fg Ag/cell) were determined after exposure of differentiated THP-1 cells to low AgNPs concentrations of 0.1 and 1.0 mg L-1, at time points of 4 and 24 h. The results were validated by mass cytometric analysis of digested cells working as a conventional inductively coupled plasma mass spectrometry, ICP-MS. This study demonstrates the power of single cell analysis by mass cytometry even for low doses experiments as a new analytical tool for hitherto unaddressed questions in nanotoxicology.
Sulfur is one of the major impurity elements in copper. Previously applied methods for the quantification of sulfur in copper and other pure metals revealed a lack of traceability and showed inconsistent result. Therefore, in this study a procedure was developed for the quantification of total sulfur in copper at low concentration levels using inductively coupled plasma-isotope dilution mass spectrometry (ICP-IDMS). A major challenge for the quantification of sulfur in copper (alloyed/unalloyed) by ICPMS is the copper matrix itself, causing matrix effects and making an extensive cleaning (cones, extraction lens) necessary after measurements. Matschat et al investigated the analysis of high-purity metals (including copper) by high resolution ICP-MS and found that the copper matrix shows strong matrix effects on the sensitivity resulting from Cu deposition on the cones. Therefore, the major part of the copper matrix has to be separated, which was accomplished by adding ammonia which forms a complex with the copper while releasing the sulfur. This was followed by a chromatographic separation using a weak cation resin. After that the sulfur fraction was further purified by chromatographic means using an anion exchange method followed by a chelating resin.
The anion exchange resin (AG1X8), however, is selective to sulfate and sulfite but less-selective to sulfide. Therefore, when quantifying total sulfur in copper, the different species of sulfur need to be oxidized to sulfate prior to the sulfur-matrix separation on the AG1X8 resin in order to avoid any measurement bias. When applying the HPA oxidation with concentrated HNO3 and H2O2 a complete conversion from sulfide and sulfite to sulfate could be achieved. The recovery of all investigated sulfur species is quantitative within measurement uncertainties. The copper samples investigated in this study contain copper in the range of 0.85-0.99 kg·kg-1 and zinc from <10 to 300 g·kg-1. Approximately 0.10-0.25 g of these samples were used to perform the sulfur-copper separation. After applying the complete three stage separation procedure the mass fractions of both elements were significantly reduced to below 400 ng·g-1 for copper and below 50 ng·g-1 for zinc, respectively. The developed procedure shows high performance, especially concerning high efficiency in matrix removal (> 99.999%) while keeping the recovery of sulfur above 80%.
The procedure blank was determined by IDMS as well and yielded values for the individual IDMS measurement sequences ranging from 3 ng to 53 ng. The average of these individual procedure blanks (n=22) was calculated and yielded a total procedure blank of 14 ng sulphur with standard deviation of 12 ng. The limit of detection (LOD, blank+3SD) calculated on this basis was 0.20 µg·g-1 while the limit of quantification (LOQ, blank+10SD) was 0.54 µg·g-1, when considering a sample weight of 0.25 g.
The quantification of low sulfur contents (< 15 µg/g) by conventional IDMS is hindered by the very high Cu/S ratio, which clearly affects the separation in a negative way: The recovery of sulfur dropped to about 30 % for four replicates, while two further replicates even showed recoveries below 10%. To enable measurement without completely changing the separation procedure, an exact amount of sulfur was added prior to spiking, such that the sulfur mass fraction was shifted to the optimum working range of the separation procedure. Thus exact amounts of sulfur were added to enhance the mass fraction of sulfur from 15 µg·g-1 to 40 µg·g-1, then the IDMS analysis was performed as usual and finally the added sulfur amount was subtracted. The so obtained measurement result agreed well with the certified value within the uncertainties. The relative expanded measurement uncertainties for conventional IDMS are below 1%. When applying the modified IDMS procedure, where back-spike is added to the sample before spiking, the relative expanded measurement uncertainties are larger and up to 5%. With the presented sulfur-matrix procedure a working range from approximately 15 µg·g-1 to 1500 µg·g-1 can be achieved.
The developed procedure for the quantification of low sulfur amounts in copper has been validated here via three different routes: first an inter-laboratory comparison at highest metrological level, second a step-by-step validation by checking each single step of the procedure and third the setup of a complete uncertainty budget.
The procedure is sufficient to facilitate value assignment of total sulfur mass fraction in reference materials. Additionally, relative measurement uncertainties were calculated below 1 % and the measurement results are traceable to the SI, which is clearly demonstrated in this work. The procedure reported in this study is a new reference procedure for sulfur measurement in copper, well meeting the requirements of the two major purposes: the certification of reference materials and the assignment of reference values for inter-laboratory comparison.
Sulfur is one of the major impurity elements in copper. Previously applied methods for the quantification of sulfur in copper and other pure metals revealed a lack of traceability and showed inconsistent result. Therefore, in this study a procedure was developed for the quantification of total sulfur in copper at low concentration levels using inductively coupled plasma-isotope dilution mass spectrometry (ICP-IDMS). A major challenge for the quantification of sulfur in copper (alloyed/unalloyed) by ICPMS is the copper matrix itself, causing matrix effects and making an extensive cleaning (cones, extraction lens) necessary after measurements. Matschat et al investigated the analysis of high-purity metals (including copper) by high resolution ICP-MS and found that the copper matrix shows strong matrix effects on the sensitivity resulting from Cu deposition on the cones. Therefore, the major part of the copper matrix has to be separated, which was accomplished by adding ammonia which forms a complex with the copper while releasing the sulfur. This was followed by a chromatographic separation using a weak cation resin. After that the sulfur fraction was further purified by chromatographic means using an anion exchange method followed by a chelating resin.
The anion exchange resin (AG1X8), however, is selective to sulfate and sulfite but less-selective to sulfide. Therefore, when quantifying total sulfur in copper, the different species of sulfur need to be oxidized to sulfate prior to the sulfur-matrix separation on the AG1X8 resin in order to avoid any measurement bias. When applying the HPA oxidation with concentrated HNO3 and H2O2 a complete conversion from sulfide and sulfite to sulfate could be achieved. The recovery of all investigated sulfur species is quantitative within measurement uncertainties. The copper samples investigated in this study contain copper in the range of 0.85-0.99 kg·kg-1 and zinc from <10 to 300 g·kg-1. Approximately 0.10-0.25 g of these samples were used to perform the sulfur-copper separation. After applying the complete three stage separation procedure the mass fractions of both elements were significantly reduced to below 400 ng·g-1 for copper and below 50 ng·g-1 for zinc, respectively. The developed procedure shows high performance, especially concerning high efficiency in matrix removal (> 99.999%) while keeping the recovery of sulfur above 80%.
The procedure blank was determined by IDMS as well and yielded values for the individual IDMS measurement sequences ranging from 3 ng to 53 ng. The average of these individual procedure blanks (n=22) was calculated and yielded a total procedure blank of 14 ng sulphur with standard deviation of 12 ng. The limit of detection (LOD, blank+3SD) calculated on this basis was 0.20 µg·g-1 while the limit of quantification (LOQ, blank+10SD) was 0.54 µg·g-1, when considering a sample weight of 0.25 g.
The quantification of low sulfur contents (< 15 µg/g) by conventional IDMS is hindered by the very high Cu/S ratio, which clearly affects the separation in a negative way: The recovery of sulfur dropped to about 30 % for four replicates, while two further replicates even showed recoveries below 10%. To enable measurement without completely changing the separation procedure, an exact amount of sulfur was added prior to spiking, such that the sulfur mass fraction was shifted to the optimum working range of the separation procedure. Thus exact amounts of sulfur were added to enhance the mass fraction of sulfur from 15 µg·g-1 to 40 µg·g-1, then the IDMS analysis was performed as usual and finally the added sulfur amount was subtracted. The so obtained measurement result agreed well with the certified value within the uncertainties. The relative expanded measurement uncertainties for conventional IDMS are below 1%. When applying the modified IDMS procedure, where back-spike is added to the sample before spiking, the relative expanded measurement uncertainties are larger and up to 5%. With the presented sulfur-matrix procedure a working range from approximately 15 µg·g-1 to 1500 µg·g-1 can be achieved.
The developed procedure for the quantification of low sulfur amounts in copper has been validated here via three different routes: first an inter-laboratory comparison at highest metrological level, second a step-by-step validation by checking each single step of the procedure and third the setup of a complete uncertainty budget.
The procedure is sufficient to facilitate value assignment of total sulfur mass fraction in reference materials. Additionally, relative measurement uncertainties were calculated below 1 % and the measurement results are traceable to the SI, which is clearly demonstrated in this work. The procedure reported in this study is a new reference procedure for sulfur measurement in copper, well meeting the requirements of the two major purposes: the certification of reference materials and the assignment of reference values for inter-laboratory comparison.
Quantification of sulphur in copper metals by isotope dilution LA-ICP-MS using polyethylene frits
(2018)
Sulphur is one of the relevant impurities in copper and its alloys affecting their material properties. To ensure the quality of copper products, fast direct solid sampling techniques are very attractive. However, for the calibration suitable matrix reference materials are required. For the certification of such reference materials appropriate, SI-traceable analytical methods are essential. Therefore, a procedure was developed to quantify total sulphur in copper by combining the classical isotope dilution (ID) technique and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS).
Here, for the first time, polyethylene (PE) frits were used to prepare appropriate solid samples for the sulphur quantification in copper metals (alloyed/unalloyed) by isotope dilution LA-ICP-MS. The properties of the PE frit meet the requirements as porous material with high absorption efficiency, thermal and chemical resistance as well as low sulphur blank. Different copper reference materials were used to develop and validate the procedure. The copper samples were spiked with 34S, digested with nitric acid and then the digests were absorbed on PE frits. After drying, the frits were analysed by LA-ICP-IDMS using a Nd:YAG laser at 213 nm coupled to an ICP sector field mass spectrometer. It could be demonstrated, that the sample solution dispersed on the frits did not influence the 32S/34S ratio significantly even though the sulphur intensities were fluctuating along the scanned lines. Relative standard deviations of the isotope ratios were below 5 % in average between three line scans (except for the pure spike solution and procedure blank). The measurement results were validated by comparing them with the results obtained by conventional ICP-IDMS after analyte-matrix separation. Plotting the mass fraction of sulphur in copper obtained by LA-ICP-IDMS versus those obtained by ICP-IDMS yields a linear curve with a correlation coefficient of 0.9999 showing a strong agreement between both techniques.
The metrological traceability to the SI from the kg down to the sulphur mass fraction in copper is established by an unbroken chain of comparisons, each accompanied by an uncertainty budget. Thus, the measurement results are considered reliable, acceptable and comparable within the stated measurement uncertainty.
In isotope ratio applications metrological principles such as measurement uncertainty and SI traceability often are not considered or realized. This is also well-documented by the traceability exception related to delta scale isotope ratio measurements CCQM requested from the CIPM. Generally, delta scale isotope ratio measurements can be performed on a precision level that is significantly lower than the uncertainty level of isotope amount ratio measurements. In the case of magnesium, we demonstrated for the first time that isotope amount ratios can be measured with uncertainties close to the typical precision of magnesium delta values, δ26/24Mg, which are at the 0.1 ‰ level.
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 NIST SRM 980 became apparent and NIST SRM 980 was replaced by an intermediate artefact, DSM3. 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. Thus, these materials qualified to establish SI-traceability for magnesium delta measurements. In a second study 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. Thus, SI traceability for magnesium isotope amount ratios and delta values is demonstrated to be established.
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.
Introducing fluorine into organic molecules leads to new chemical/physical properties. Up to now, the OECD identified and categorized 4730 per- and polyfluoroalkyl substances-related CAS numbers. Especially in the field of technical applications (e.g. surface coatings, fire extinguishing foams) as well as pharmaceuticals, fluorinated substances gain in importance. Thus, an increasing release of fluorinated compounds into the environment is expected.
The high environmental persistence of perfluorinated compounds leads to the risk of bioaccumulation. Partially fluorinated substances (polyfluorinated compounds) undergo degradation; thus, further possible fluorine species occur, which may exhibit different toxic/chemical properties. However, current target methods (e.g., HPLC/MS-MS) are not applicable for a comprehensive screening as well as assessment of pollution.
Thus, the poster presents a new sum parameter method for quantitative determination of extractable organically bound fluorine (EOF) in surface water samples. The method is based on solid-phase extraction (SPE) for fluorinated compounds as well as quantitative separation of interfering inorganic fluoride in combination with high-resolution-continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS) for quantitative analysis. By means of this technique, the detection of high resolution molecular absorption spectra (MAS) is enabled upon the addition of a modifier and the formation of a diatomic molecule (e.g. GaF)
After successful optimization of the SPE procedure (maximum concentration of extractable organic fluorine), enrichment factors of about 1000 were achieved, allowing for highly sensitive fluorine detection. Next to a species-unspecific response, limits of detection in the low nanogram per liter range were achieved and real surface water samples were analyzed. EOF values in the range of about 50-300 ng/L were detected.
The developed method allows for a fast and sensitive as well as selective screening of organically bound fluorine (EOF) in surface water samples, helping to elucidate pollution hotspots as well as discharge routes.
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.
Nanoparticles (NPs) have found a wide range of applications in research and industry. Thereby the interaction of NPs with biological systems like cells has become a major field of interest, ranging from medical applications to nanotoxicology. Size, shape and surface modification of the nanomaterials determine the uptake rate and pathway into the cells, and therefore impact specific cell components and processes.
Inductively coupled plasma mass spectrometry (ICP-MS) is a well-established analytical method offering high sensitivity and multi-element capability. By coupling a laser ablation (LA) system to an ICP-MS the analysis of different kinds of solid samples is possible. In recent years, it was shown that LA-ICP-MS can provide quantitative as well as distribution information of metal containing nanoparticles (NPs) in cell samples.
Here LA-ICP-MS was applied for the imaging of individual fibroblast cells to study the uptake and intracellular processing of NPs. Our results show that LA-ICP-MS can be used to localize nanoparticle aggregates within cellular compartments. The studied NPs accumulate in the perinuclear region in the course of intracellular processing, but do not enter the cell nucleus. The uptake efficiency depends strongly on the physico-chemical properties of the nanostructures as well as on the incubation conditions like concentration and incubation time.
ICP-MS was used to determine the composition of the nanomaterials as well as the number of NPs in cells after acid digestion of the samples.
Nanoparticles (NPs) have found a wide range of applications in research and industry. Thereby the interaction of NPs with biological systems like cells has become a major field of interest, ranging from medical applications to nanotoxicology. Size, shape and surface modification of the nanomaterials determine the uptake rate and pathway into the cells, and therefore impact specific cell components and processes.
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is an established quantitative multi-elemental analysis and mapping technique. In recent years, it was shown that LA-ICP-MS can provide quantitative as well as distribution information of metal containing nanoparticles (NPs) in cell samples.
Here LA-ICP-MS was applied for the imaging of individual fibroblast cells to study the uptake and intracellular processing of NPs. Our results show that LA-ICP-MS can be used to localize nanoparticle aggregates within cellular compartments. The studied NPs accumulate in the perinuclear region in the course of intracellular processing, but do not enter the cell nucleus. The uptake efficiency depends strongly on the physico-chemical properties of the nanostructures as well as on the incubation conditions like concentration and incubation time.
ICP-MS was used to determine the composition of the nanomaterials as well as the number of NPs in cells after acid digestion of the samples.
Contamination of the environment with antibiotics is of great concern as it promotes the evolution of antimicrobial resistances. In case of amoxicillin (AMX) in the aquatic environment, further risk arises from hydrolysis products (HPs) which can cause allergy. To assess these risks, a comprehensive investigation and understanding of the degradation of AMX is necessary. We investigated the hydrolysis rate of AMX in different types of water as well as the influence of temperature and irradiation. The content of the heavy metal ions copper and zinc was found to be crucial for the hydrolysis rate of AMX and stability of HPs. Eventually, a new degradation pathway for AMX could be elaborated and confirmed by tandem mass spectrometry (LC-MS/MS).
In addition to previously reported results on the accelerated weathering of polystyrene samples (PS) containing 1 wt.% hexabromocyclododecane (HBCD), we present the first results of our investigations of polypropylene samples (PP) containing 0.1 wt.% BDE-209. All studied polymer samples were exposed to a defined weathering schedule in a climate chamber in accordance to regulation EN ISO 4892-3:2006. For the determination of BDE-209 in the collected raining water the samples were prepared in accordance to a validated protocol. Before the analyses each sample was spiked with isotopically labeled BDE-209. Subsequently the samples were extracted with isooctane. The obtained extracts were concentrated, and the resulting solutions were analyzed by GC/MS. Additionally, the total bromine content was monitored for the weathered and untreated samples using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and X-ray fluorescence analysis (XRF) as a non-destructive and rapid method. In general, the resulting data from the accelerated weathering will be compared to those from the natural weathering experiments. Here, the surfaces of the test pieces were analyzed by LA-ICP-MS and XRF as well. Moreover, soil bed tests were conducted in a well characterized model soil. This soil (boulder-clay, sand with 12 % loam, particle size in total 0.2-4 mm) is filled in a free-draining basin inside of an air-conditioned cellar. In this manner, TOC, water capacity and humidity are recorded parameters. To induce a leaching process from the samples by the raining water, the target water content is calculated to 8%. The actual humidity is measured by a tensiometer, assuring the duration of the raining period. A defined humidity is a fundamental parameter for a biological activity in the soil. The test polymers were placed up to the half in the soil. Microbial activity of the soil is monitored by a reference polymer (polyurethane) and should induce the release of HBCD and BDE-209 out of the test materials. These released analytes will be captured by passive samplers (silicone tubes) placed in a distinct distance to the polymer samples in the soil. The soil bed experiments are complementary to the weathering experiments due to the biological activity in the soil.