The Experts below are selected from a list of 88173 Experts worldwide ranked by ideXlab platform
Pingan Peng - One of the best experts on this subject based on the ideXlab platform.
-
compound specific stable carbon isotope analysis of hexabromocyclododecane diastereoisomers using gas chromatography isotope ratio mass spectrometry
Rapid Communications in Mass Spectrometry, 2019Co-Authors: Gen Cheng, Shutao Gao, Yang Gao, Pingan PengAbstract:RATIONALE Compound-specific stable isotope analysis (CSIA) is a powerful tool for the source apportionment and characterization of Environmental Transformation processes, especially for new emerging contaminants. In this study, we have developed an effective method for determination of the stable carbon isotope ratios of hexabromocyclododecane diastereoisomers. METHODS Three diastereoisomers of hexabromocyclododecane (HBCD), α-, β-, and γ-HBCD, were separated on a preparative high-performance liquid chromatography (HPLC) system. Their carbon isotope ratios were determined using gas chromatography/isotope ratio mass spectrometry (GC/IRMS), and compared with data obtained by elemental analyzer/isotope ratio mass spectrometry (EA/IRMS). RESULTS α-, β-, and γ-HBCD were well separated by the preparative HPLC system. Method validation results indicated excellent precision and reproducibility. For a series of injection volumes (0.5 to 3 μL), the average carbon isotope ratios for α-HBCD, β-HBCD, and γ-HBCD were -26.42‰, -26.88‰, and -26.43‰, respectively, and their deviations from those of the HBCD standard (-26.52‰) were all lower than the analytical uncertainty of 0.5‰. Relative standard deviations of intra-day and inter-day injections of HBCD were in the ranges 0.35-0.64% and 0.37-0.76%, respectively. Comparison with EA/IRMS further verified the accuracy of the HBCD stable carbon isotope ratio measured by GC/IRMS. CONCLUSIONS This work offers a novel approach to separate and concentrate the three major isomers of HBCD and to determine their stable carbon isotope ratios. This permits analysis of their carbon isotope ratios in Environmental samples in order to elucidate the sources and abiotic or biological Transformation processes of HBCD in the environment.
Zijian Wang - One of the best experts on this subject based on the ideXlab platform.
-
2 4 dichloro 6 nitrophenol a photonitration product of 2 4 dichlorophenol caused anti androgenic potency in chinese rare minnows gobiocypris rarus
Environmental Pollution, 2016Co-Authors: Rui Chen, Cao Liu, Lilai Yuan, Jinmiao Zha, Zijian WangAbstract:2,4-Dichloro-6-nitrophenol (DCNP) is an Environmental Transformation product of 2,4-dichlorophenol that has been identified as widespread in effluent wastewater, but little is known about its toxicity because this compound is not regulated. Therefore, to investigate the endocrine disruption potency of DCNP in Chinese rare minnows (Gobiocypris rarus), adult and juvenile fish were exposed to various concentrations of DCNP (2, 20, and 200 μg/L) for 28 d. After 28 d exposure, the plasma vitellogenin (VTG) levels were reduced in females while increased in males and juvenile fish considerably, as compared with the control. These results suggested that DCNP affects the HPG-axis in a sex-dependent way. Testosterone (T) levels in the plasma were significantly lower in adult and juvenile fish and were accompanied by an increased estradiol (E2)/T ratio. Histopathological observation revealed hypertrophy of the hepatocytes and nuclear pyknosis in the liver, the inhibition of spermatogenesis in the testes, and the degeneration of oocytes in the ovaries after DCNP exposure. The expression pattern of selected genes indicated that the nuclear receptor, steroidogenesis and gonadotropin regulation pathways were perturbed after DCNP exposure. Above all, our results demonstrated that DCNP clearly had anti-androgenic activity in both adult and juvenile fish and can therefore be considered as an endocrine-disrupting chemical.
Martin Elsner - One of the best experts on this subject based on the ideXlab platform.
-
calibration bias of experimentally determined chlorine isotope enrichment factors the need for a two point calibration in compound specific chlorine isotope analysis
Rapid Communications in Mass Spectrometry, 2017Co-Authors: Karin Ebert, Martin Elsner, Christine Laskov, Stefan B HaderleinAbstract:Rationale The recent development of compound-specific online chlorine isotope analysis (37Cl-CSIA) methods has fostered dual chlorine–carbon isotope studies to gain better insights into sources and Environmental Transformation reactions of chlorinated ethenes. One-point and two-point calibration schemes are currently used to convert raw data to the international δ37ClSMOC scale, but a critical evaluation of best practices to arrive at reliable δ37ClSMOC signatures and enrichment factors was missing and is presented here. Methods Aqueous solutions of neat perchloroethylene and trichloroethylene (TCE) and aqueous samples from a TCE biodegradation experiment with pure cultures of Desulfitobacterium hafniense Y51 were analysed for their chlorine isotope ratios using GC/qMS and GC/IRMS. The δ37ClSMOC values were obtained using one-point and two-point calibration schemes. Chlorine isotope enrichment factors, eCl, were calculated using both approaches and the corresponding bias of δ37ClSMOC values introduced by the different types of calibration was determined. Results Different calibration methods resulted in significant differences (up to 30%) in both δ37Cl signatures and eCl values. Conclusions Our results demonstrate that a two-point calibration together with comprehensive information on reference materials is indispensable and should become standard practice for reliable 37Cl-CSIA of organic compounds. Copyright © 2016 John Wiley & Sons, Ltd.
-
stable isotope fractionation to investigate natural Transformation mechanisms of organic contaminants principles prospects and limitations
Journal of Environmental Monitoring, 2010Co-Authors: Martin ElsnerAbstract:Gas chromatography–isotope ratio mass spectrometry (GC-IRMS) has made it possible to analyze natural stable isotope ratios (e.g., 13C/12C, 15N/14N, 2H/1H) of individual organic contaminants in Environmental samples. They may be used as fingerprints to infer contamination sources, and may demonstrate, and even quantify, the occurrence of natural contaminant Transformation by the enrichment of heavy isotopes that arises from degradation-induced isotope fractionation. This review highlights an additional powerful feature of stable isotope fractionation: the study of Environmental Transformation mechanisms. Isotope effects reflect the energy difference of isotopologues (i.e., molecules carrying a light versus a heavy isotope in a particular molecular position) when moving from reactant to transition state. Measuring isotope fractionation, therefore, essentially allows a glimpse at transition states! It is shown how such position-specific isotope effects are “diluted out” in the compound average measured by GC-IRMS, and how a careful evaluation in mechanistic scenarios and by dual isotope plots can recover the underlying mechanistic information. The mathematical framework for multistep isotope fractionation in Environmental Transformations is reviewed. Case studies demonstrate how isotope fractionation changes in the presence of mass transfer, enzymatic commitment to catalysis, multiple chemical reaction steps or limited bioavailability, and how this gives information about the individual process steps. Finally, it is discussed how isotope ratios of individual products evolve in sequential or parallel Transformations, and what mechanistic insight they contain. A concluding session gives an outlook on current developments, future research directions and the potential for bridging the gap between laboratory and real world systems.
Gen Cheng - One of the best experts on this subject based on the ideXlab platform.
-
compound specific stable carbon isotope analysis of hexabromocyclododecane diastereoisomers using gas chromatography isotope ratio mass spectrometry
Rapid Communications in Mass Spectrometry, 2019Co-Authors: Gen Cheng, Shutao Gao, Yang Gao, Pingan PengAbstract:RATIONALE Compound-specific stable isotope analysis (CSIA) is a powerful tool for the source apportionment and characterization of Environmental Transformation processes, especially for new emerging contaminants. In this study, we have developed an effective method for determination of the stable carbon isotope ratios of hexabromocyclododecane diastereoisomers. METHODS Three diastereoisomers of hexabromocyclododecane (HBCD), α-, β-, and γ-HBCD, were separated on a preparative high-performance liquid chromatography (HPLC) system. Their carbon isotope ratios were determined using gas chromatography/isotope ratio mass spectrometry (GC/IRMS), and compared with data obtained by elemental analyzer/isotope ratio mass spectrometry (EA/IRMS). RESULTS α-, β-, and γ-HBCD were well separated by the preparative HPLC system. Method validation results indicated excellent precision and reproducibility. For a series of injection volumes (0.5 to 3 μL), the average carbon isotope ratios for α-HBCD, β-HBCD, and γ-HBCD were -26.42‰, -26.88‰, and -26.43‰, respectively, and their deviations from those of the HBCD standard (-26.52‰) were all lower than the analytical uncertainty of 0.5‰. Relative standard deviations of intra-day and inter-day injections of HBCD were in the ranges 0.35-0.64% and 0.37-0.76%, respectively. Comparison with EA/IRMS further verified the accuracy of the HBCD stable carbon isotope ratio measured by GC/IRMS. CONCLUSIONS This work offers a novel approach to separate and concentrate the three major isomers of HBCD and to determine their stable carbon isotope ratios. This permits analysis of their carbon isotope ratios in Environmental samples in order to elucidate the sources and abiotic or biological Transformation processes of HBCD in the environment.
Rui Chen - One of the best experts on this subject based on the ideXlab platform.
-
2 4 dichloro 6 nitrophenol a photonitration product of 2 4 dichlorophenol caused anti androgenic potency in chinese rare minnows gobiocypris rarus
Environmental Pollution, 2016Co-Authors: Rui Chen, Cao Liu, Lilai Yuan, Jinmiao Zha, Zijian WangAbstract:2,4-Dichloro-6-nitrophenol (DCNP) is an Environmental Transformation product of 2,4-dichlorophenol that has been identified as widespread in effluent wastewater, but little is known about its toxicity because this compound is not regulated. Therefore, to investigate the endocrine disruption potency of DCNP in Chinese rare minnows (Gobiocypris rarus), adult and juvenile fish were exposed to various concentrations of DCNP (2, 20, and 200 μg/L) for 28 d. After 28 d exposure, the plasma vitellogenin (VTG) levels were reduced in females while increased in males and juvenile fish considerably, as compared with the control. These results suggested that DCNP affects the HPG-axis in a sex-dependent way. Testosterone (T) levels in the plasma were significantly lower in adult and juvenile fish and were accompanied by an increased estradiol (E2)/T ratio. Histopathological observation revealed hypertrophy of the hepatocytes and nuclear pyknosis in the liver, the inhibition of spermatogenesis in the testes, and the degeneration of oocytes in the ovaries after DCNP exposure. The expression pattern of selected genes indicated that the nuclear receptor, steroidogenesis and gonadotropin regulation pathways were perturbed after DCNP exposure. Above all, our results demonstrated that DCNP clearly had anti-androgenic activity in both adult and juvenile fish and can therefore be considered as an endocrine-disrupting chemical.