Chemische Charakterisierung und Spurenanalytik
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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.
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.
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.
Online coupling of electrochemistry with mass spectrometry (EC/MS) is highly promising for prediction and simulation of metabolic processes of xenobiotics in living organisms. Less time and cost of analysis, matrix free detection, and automation make EC/MS-based metabolomics superior over traditional in-vivo and in-vitro methods. Furthermore, EC/MS has a special feature to identify reactive intermediates and reaction mechanisms.
The main objective of this work was to simulate biotransformation processes of pesticides by EC/MS and to elucidate the Transformation products (TPs). We have studied the oxidative phase I metabolism processes of selected pesticides by EC/MS or with liquid chromatography (EC/LC/MS) and compared the derived TPs with cytochrome based metabolites. The electrochemical TPs were produced by boron-doped diamond electrode, separated by LC, and detected by single quadrupole ESI-MS online. Structural identification of both electrochemical oxidation and liver microsome metabolites were based on accurate mass measurements by FT-ICR high-resolution mass spectrometry, isotopic pattern, MS/MS fragmentation, and Retention time alignments.
Main phase I oxidative metabolites by P-oxidation, N- & O- dealkylation, dechlorination, hydroxylation, and -OH- oxidation have been identified. Many targeted and untargeted metabolites have been identified by EC/(LC)/MS. Additionally, reactive species have been trapped online by biomolecules to study phase II conjugative reactions. Furthermore, we synthesized TP standards by EC/MS and applied them for pesticide's TPs occurrence investigation in foodstuf matrices.
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 addition to previously reported results on the simulated aging of polystyrene samples (PS) containing 1 wt. % hexabromocyclododecane (HBCD), we present the first results of our investigations of polypropylene (PP)-samples 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 rain water samples derived from the used climate chamber, the samples were prepared in accordance with a validated protocol. Before the analyses, each sample was spiked with 2 µL of isotopically labeled BDE-209 (13C10-BDE-209) to serve as internal standard (ISTD) in the performed stable isotope dilution analysis. Subsequently the samples were extracted with isooctane, the obtained aliquots of the extracts were concentrated to 200 µL and 2 µL of the resulting solution were injected to the GC/MS for quantification.
Additionally, the total bromine contents are monitored for the aged and untreated samples using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) as well as X-ray fluorescence analysis (XRF) as non-destructive and rapid method. Furthermore, results from surface analysis using environmental scanning electron microscopy (ESEM) for morphological characterization of the aged and untreated samples were presented and discussed. In general, the resulting data from the accelerated aging will be compared to those from the natural weathering experiments (“atmospheric exposure”, in soil).
The atmospheric exposure was performed by placing the samples on a weathering rack, which is aligned in SW direction (in a 45° angle to the horizon). The weathering data were regularly recorded by Deutscher Wetterdienst at this site. The surfaces of the test specimens (aged and stored references) were analyzed by ESEM as well as by LA-ICP-MS and by XRF. The surface of PS and PP specimens aged outdoors present the aging under real conditions and allow the comparison to the accelerated aged specimens by means of the weathering chamber. This way, we explore the efficiency of the accelerated aging procedure, which provides the advantage of well-defined and reproducible conditions compared to natural weathering, as a tool for testing different plastic materials.
Additionally “in soil” experiments were conducted in-door in a well characterized testing soil. The soil (boulder-clay, sand with 12 % loam, particle size in total 0.2-4 mm) is filled in a free-draining concrete basin inside of an air-conditioned room. In this manner, TOC, water capacity and humidity are recorded parameters. To assure a washing out 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. The water content is additionally monitored by weight of the basin, capturing water from raining periods. The correct humidity is a fundamental parameter for biological activity. Samples of PS resp. PP were of dimension 10x1cm and 5 specimens were placed up to the half in the soil per basin. Microbial activity of the soil, monitored by the reference polyurethane, sets HBCD resp. BDE-209 of the samples free and will be leached from the samples by raining water. Thereafter these will be captured by passive samplers placed in a distinct distance to the samples in the soil. The “in soil” experiments are complementary to the weathering experiments due to the biological activity in the soil. These experiments simulate the fate of the brominated flame retardants in the biosphere.
Diclofenac (DCF) is a widely used drug against fever, inflammation, pain, and rheumatic diseases. An average of 70 % of the ingested diclofenac is excreted in the urine. Thus, 63 tons per year are introduced into the water cycle in Germany. Due to insufficient removal of diclofenac in wastewater treatment plants, residues of diclofenac can be found in surface water and sometimes in drinking water. In order to establish an immunoassay, an anti-DCF antibody was required. Some antibody developments have been reported, based on an immunogen resulting from direct coupling of diclofenac to proteins via the carboxylic function. Finally, we used a monoclonal antibody, clone F01G21.
Carbamazepine (CBZ) and cetirizine (CTZ) are pharmaceutical drugs detected in the aquatic environment. However, the effects to marine invertebrates derived from the combination of these drugs with decreased pH conditions due to ocean acidification are poorly explored. This study investigated the biochemical parameters related to metabolic capacity and oxidative stress response and the transcription of genes related to the mode of action (MoA) of CBZ (1.0 μg/L) and CTZ (0.6 μg/L) in the clam Ruditapes philippinarum chronically exposed (28 days) to control (7.8) and low (7.5) pH conditions. The biochemical parameters applied were: the activity of electron transport system (indicator of organisms’ metabolic capacity); lipid peroxidation content (indicator of cell damage); total glutathione peroxidase activity (indicator of antioxidant defense). The transcription of genes related with drug neurotransmission and metabolism, cell defense and immunity and biomineralization was studied. No metabolic changes and oxidative stress was induced by the exposure to CBZ or CTZ at each pH level, but the transcription of several genes related with the MoA (neurotransmission, immunity and biomineralization) was altered by low pH, drug exposure and the combination of both stressors. In conclusion, it was shown that the interaction of drug exposure and low pH conditions can change bivalves’ sensitivity to drugs or alter drugs toxicity.