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Arsenolipids (AsL) of the type arsenic-containing fatty acids (AsFA) and hydrocarbons (AsHC) are natural organoarsenic compounds present in high abundance in seafood. Since little is known about their toxicity, there is a significant concern about their health risk. Here we report the synthesis of two new AsL and their identification in fish by liquid chromatography (LC) coupled simultaneously to inductively coupled plasma mass spectrometry (ICP-MS) and to high resolution mass spectrometry (HR-MS). The molecular structure was elucidated on the basis of their exact mass and their product ion mass spectra. One of the synthesized AsL has been already identified in fish samples, meanwhile, the other arsenolipid is reported here as a natural product in fish.
The present study was focused on the determination and identification of arsenic species in methanolic extracts of cod liver. Arsenic species were fractionated and the fractions analysed by RP-HPLC-ICP-MS coupled with ESI-Q-TOF-MS. The total concentration of arsenic in the fresh cod liver was analysed by ICP-MS to be 1.53 ± 0.02 mg As kg-1 w.w. and the extraction recovery was ca. 100% and the column recovery >93%. Besides polar inorganic and methylated arsenic species (>70%) more hydrophobic arsenic-containing fatty acids and hydrocarbons occurred. Based on the mass spectrometric data proposals for molecular structures were elaborated for 20 of the organic As species included 10 arsenic-containing fatty acids (AsFA) and an arsenic-containing hydrocarbon (AsHC) mentioned for the first time in fresh cod liver. Arsenobetaine was found as main water-soluble arsenic compound in cod liver followed by higher molecular mass arsenic-containing fatty acids and hydrocarbons.
Arsenolipids (AsL) of the type arsenic-containing fatty acids (AsFA) and hydrocarbons (AsHC) are known to occur in seafood and their identification is today a challenge due to the need of data for toxicological assessment. The aim of this investigation was to enhance the data concerning AsL in commercial canned cod liver. Therefore, the present study focuses on the quantification and identification of AsL by LC–ICP-MS combined with ESI-MS. The molecular structure of 17 AsL was elucidated on the basis of their exact mass and their product ion spectra and two new AsFA tentatively identified. The total arsenic concentration in four different canned cod liver analyzed by ICP-MS ranged from 2.6 to 5.5 mg As/kg with an extraction recovery of 98%. The AsL detected by RP-IPC–MS comprise 58–95% of the total arsenic content, indicating that AsL are a major class of arsenic in canned cod liver. Much of the AsL detected in the canned cod liver extracts are, however, not yet identified.
Practical applications: The results obtained in the present research show the possibility to apply the current extraction and detection method in different biological samples for the determination of AsL. Additionally, this information can be used for further studies to assess the risk of AsL for consumer health. On the other hand, the MS/MS results could be used for the future identification of AsL without the ICP-MS detection and thus, low the cost of the analysis.
Arsenic and mercury are frequent contaminants in the environment and care must be taken to limit their entrance into the food chain. The toxicity of both elements strongly depends upon their speciation. Total amounts of As and Hg as well as their species were analyzed in muscle and liver of 26 fishes of seven freshwater fish species caught in the River Elbe. The median concentrations of As were 162 mg kg-1 w.w. in liver and 92 mg kg-1 w.w. in muscle. The median concentrations of total Hg were 241 mg kg-1 w.w. in liver and 256 mg kg-1 w.w. in muscle. While this level of Hg contamination of the freshwater fish in the River Elbe is significantly lower than 20 years ago, it exceeds the recommended environmental Quality standard of 20 mg Hg kg-1 w.w. by a factor of 5e50. However, the European maximum level of 500 mg Hg kg-1 for fish for human consumption is rarely exceeded. Arsenic-containing fatty acids and hydrocarbons were determined and partially identified in methanolic extracts of the fish by HPLC coupled in parallel to ICP-MS (element specific detection) and ESI-Q-TOF-MS (molecular structure detection). While arsenobetaine was the dominant As species in the fish, six arsenolipids were detected and identified in the extracts of liver tissue in common bream (Abramis brama), die (Leuciscus idus), asp (Aspius aspius) and northern pike (Esox lucius). Four arsenic-containing fatty acids (AsFA) and two arsenic-containing hydrocarbons (AsHC) are reported in freshwater fish for the first time. With respect to mercury the more toxic MeHgþ was the Major species in muscle tissue (>90% of total Hg) while in liver Hg2þ and MeHgþ were of equal importance. The results Show the high relevance of element speciation in addition to the determination of total element concentrations to correctly assess the burden of these two elements in fish.
The potential release of hazardous substances from polymer-based products is currently in the focus of environmental policy. Environmental simulations are applied to expose such products to selected aging conditions and to investigate release processes. Commonly applied aging exposure types such as solar and UV radiation in combination with water contact, corrosive gases, and soil contact as well as expected general effects on polymers and additional ingredients of polymer-based products are described. The release of substances is based on mass-transfer processes to the material surfaces. Experimental approaches to investigate transport processes that are caused by water contact are presented. For tailoring the tests, relevant aging exposure types and release quantification methods must be combined appropriately. Several studies on the release of hazardous substances such as metals, polyaromatic hydrocarbons, flame retardants, antioxidants, and carbon nanotubes from polymers are summarized exemplarily. Differences between natural and artificial exposure tests are discussed and demonstrated for the release of flame retardants from several polymers and for biocides from paints. Requirements and limitations to apply results from short-term artificial environmental exposure tests to predict long-term environmental behavior of polymers are presented.
High polarity analyte(s) in aqueous media: determination of L-PFOA and L-PFOS in ground water
(2022)
The CCQM-K156 comparison was coordinated by TUBITAK UME on behalf of the Organic Analysis Working Group (OAWG) of the Comité Consultatif pour la Quantité de Matière (CCQM) for National Measurement Institutes (NMIs) and Designated Institutes (DIs) which provide measurement services in organic analysis under the 'Comité International des Poids et Mesures' Mutual Recognition Arrangement (CIPM MRA).
Perfluoro alkyl substances (PFAS) such as PFOS and PFOA have been used in numerous industrial applications and products. Because of their high stability and resistance to biodegradation, atmospheric photooxidation, direct photolysis and hydrolysis, they are extremely persistent in the environment. The European Union (EU) Water Framework Directive lists PFOS as a priority hazardous substance that poses a significant risk to the aquatic environment. The use of PFOS-containing Aqueous Film-Forming Foams (AFFFs) has been banned since June 2011 in the EU. As relatively water-soluble, effectively non-degradable compounds, PFOS and PFOA migrate to ground water. They are not removed in the conventional drinking water treatment, and therefore cause health risks in polluted areas. The EU Drinking Water Directive and the European Commission has proposed a limit value of 100 ng/L for the sum of 20 PFAS, including PFOS and PFOA.
This study provides the means for assessing measurement capabilities for determination of high polarity measurands in a procedure that requires extraction, clean-up, analytical separation and detection. Successful participation in CCQM-K156 demonstrates measurement capabilities in determining mass fraction of organic compounds, with a molecular mass of 200 g/mol to 700 g/mol, having high polarity pKow -2, in a mass fraction range from 0.5 ng/kg to 500 ng/kg in aqueous media.
Nine NMIs and DIs participated in the CCQM-K156 key comparison. Seven institutes reported their results. SPE was applied in the sample pre-treatment and LC-MS was applied for detection. All participating laboratories applied isotope dilution mass spectrometry (IDMS) techniques for quantification. Participants established the metrological traceability of their results using certified reference materials (CRMs) from NMIs with stated traceability; where commercially available high purity materials were used the purity was determined in-house. The CCQM-K156 results for L-PFOA and L-PFOS range from 2.75 ng/kg to 5.50 ng/kg with a % RSD of 19.5 % for L-PFOA and from 2.04 ng/kg to 4.45 ng/kg with a % RSD of 21.3 % for L-PFOS. The KCRV was assigned using a Hierarchical Bayesian Random Effects Model (HB REM) estimator from the values reported by six of the participants. One participant result of L-PFOS and one result of L-PFOA were excluded from the KCRV for technical reasons. The KCRV was 4.9 ng/kg ± 0.4 ng/kg for L-PFOA and 3.8 ng/kg ± 0.4 ng/kg for L-PFOS. The six institutes that were included in the assignment of consensus KCRV all agreed within their standard uncertainties.
To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.
The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
Hands-off linear interaction energy approach to binding mode and affinity estimation of estrogens
(2013)
With this work we target the development of a predictictive model for the identification of small molecules which bind to the estrogen receptor alpha and, thus, may act as endocrine disruptors. We propose a combined thermodynamic approach for the estimation of preferential binding modes along with corresponding free energy differences using a linear interaction energy (LIE) ansatz. The LIE model is extended by a Monte Carlo approach for the computation of conformational entropies as recently developed by our group. Incorporating the entropy contribution substantially increased the correlation with experimental affinity values. Both squared coefficients for the fitted data as well as the more meaningful leave-one-out cross-validation of predicted energies were elevated up to rFit2 = 0.87 and qLOO2 = 0.82, respectively. All calculations have been performed on a set of 31 highly diverse ligands regarding their structural properties and affinities to the estrogen receptor alpha. Comparison of predicted ligand orientations with crystallographic data retrieved from the Protein database pdb.org revealed remarkable binding mode predictions.
The title compound (AHTN-OH), C17H26O, was prepared in order to provide standard materials for the qualitative and quantitative analysis of environmental pollutants. The molecule possesses a chiral C atom, although the structure determination was performed on racemic material, expressed in the structure as disordered chiral sites. The asymmetric unit consists of four AHTN-OH molecules containing an hydroxy group and forming a tetrameric cyclic motif built up by four strong hydrogen bonds between these hydroxy groups and additionally by two weak C–H···π interactions. Furthermore, these tetramers are linked via very weak C–H···π interactions, forming chains along the c axis.
A recently introduced inductively coupled plasma-time-of-flight-mass spectrometer (ICP-ToF-MS) shows enhanced sensitivity compared to previous developments and superior isotope ratio precision compared to other ToF and commonly used single-collector ICP-MS instruments. Following this fact, an improvement for isotope dilution ICP-MS using the new instrumentation has been reported. This study aimed at investigating whether this improvement also meets the requirements of species-specific isotope dilution using GC/ICP-MS, where short transient signals are recorded. The results of the analysis of monomethylmercury (MMHg) of a sediment reference material show that isotope ratio precision of ICP-MS instruments equipped with quadrupole, sector-field, and time-of-flight mass analyzers is similar within a broad range of peak signal-to-noise ratio when analyzing one isotopic system. The procedural limit of quantification (LOQ) for MMHg, expressed as mass fraction of Hg being present as MMHg, w(Hg)MMHg, was similar as well for all investigated instruments and ranged between 0.003 and 0.016 μg/kg. Due to the simultaneous detection capability, the ICP-ToF-MS might, however, be more favorable when several isotopic systems are analyzed within one measurement. In a case study, the GC/ICP-ToF-MS coupling was applied for analysis of MMHg in sediments of Finow Canal, a historic German canal heavily polluted with mercury. Mass fractions between 0.180 and 41 μg/kg (w(Hg)MMHg) for MMHg, and 0.056 and 126 mg/kg (w(Hg)total) for total mercury were found in sediment samples taken from the canal upstream and downstream of a former chemical plant.