Effect-Directed Analysis of Aryl Hydrocarbon Receptor Agonists in Sediments from the Three Gorges Reservoir, China.

The construction of the Three Gorges Dam (TGD) in the Yangtze River raises great concern in ecotoxicological research since large amounts of pollutants enter the Three Gorges Reservoir (TGR) water bodies after TGD impoundment. In this work, effect-directed analysis (EDA), combining effect assessment, fractionation procedure, and target and nontarget analyses, was used to characterize aryl hydrocarbon receptor (AhR) agonists in sediments of the TGR. Priority polycyclic aromatic hydrocarbons (PAHs) containing four to five aromatic rings were found to contribute significantly to the overall observed effects in the area of Chongqing. The relatively high potency fractions in the Kaixian area were characterized by PAHs and methylated derivatives thereof and heterocyclic polycyclic aromatic compounds (PACs) such as dinaphthofurans. Benzothiazole and derivatives were identified as possible AhR agonists in the Kaixian area based on nontarget liquid chromatography-high resolution mass spectrometry (LC-HRMS). To our knowledge, this study is the first one applying the EDA approach and identifying potential AhR agonists in TGR.

Root uptake and metabolization of Alternaria toxins by winter wheat plants using a hydroponic system.

Fungi of the genus Alternaria are ubiquitous in the environment. Their mycotoxins can leach out of contaminated plants or crop debris into the soil entering the plant via the roots. We aim to evaluate the importance of this entry pathway and its contribution to the overall content of Alternaria toxins (ATs) in wheat plants to better understand the soil-plant-phytopathogen system. A hydroponic cultivation system was established and wheat plants were cultivated for up to two weeks under optimal climate conditions. One half of the plants was treated with a nutrient solution spiked with alternariol (AOH), alternariol monomethyl ether (AME), and tenuazonic acid (TeA), whereas the other half of the plants was cultivated without mycotoxins. Plants were harvested after 1 and 2 weeks and analyzed using a QuEChERS-based extraction and an in-house validated LC-MS/MS method for quantification of the ATs in roots, crowns, and leaves separately. ATs were taken up by the roots and transported throughout the plant up to the leaves after 1 as well as 2 weeks of cultivation with the roots showing the highest ATs levels followed by the crowns and the leaves. In addition, numerous AOH and AME conjugates like glucosides, malonyl glucosides, sulfates, and di/trihexosides were detected in different plant compartments and identified by high-resolution mass spectrometry. This is the first study demonstrating the uptake of ATs in vivo using a hydroponic system and whole wheat plants examining both the distribution of ATs within the plant compartments and the modification of ATs by the wheat plants.

Cetirizine as pH-dependent cross-reactant in a carbamazepine-specific immunoassay.

High performance liquid chromatography (HPLC) was hyphenated with a previously reported carbamazepine-specific enzyme-linked immunosorbent assay (ELISA) as a screening approach to water analysis in order to identify possible interferences from transformation products. Treated wastewater was analysed and three substances were recognized by the antibody besides carbamazepine: the metabolites 10,11-dihydro-10,11-epoxycarbamazepine and 2-hydroxycarbamazepine plus the structurally not obviously related antihistamine cetirizine. The molar cross-reactivity against cetirizine was found to be pH-dependent and assessed to be 400% at pH 4.5 and 22% at pH 10.5. Performing the ELISA at pH 10.5 greatly improved the accuracy when carbamazepine was determined in surface and wastewater samples.

Monitoring carbamazepine in surface and wastewaters by an immunoassay based on a monoclonal antibody.

The pharmaceutical compound carbamazepine (CBZ) is an emerging pollutant in the aquatic environment and may potentially be used as a wastewater marker. In this work, an enzyme-linked immunosorbent assay (ELISA) for the detection of carbamazepine in surface and sewage waters has been developed. The heterogeneous immunoassay is based on a commercially available monoclonal antibody and a novel enzyme conjugate (tracer) that links the hapten via a hydrophilic peptide (triglycine) spacer to horseradish peroxidase. The assay achieves a limit of detection of 24 ng/L and a quantitation range of 0.05-50 microg/L. The analytical performance and figure of merits were compared to liquid chromatography-tandem mass spectrometry after solid-phase extraction. For nine Berlin surface water samples and one wastewater sample, a close correlation of results was observed. A constant overestimation relative to the CBZ concentration of approximately 30% by ELISA is probably caused by the presence of 10,11-epoxy-CBZ and 2-hydroxy-CBZ in the samples. The ELISA displayed cross-reactivities for these compounds of 83% and 14%, respectively. In a first screening of 27 surface water samples, CBZ was detected in every sample with concentrations between 0.05 and 3.2 microg/L. Since no sample cleanup is required, the assay allowed for the determination of carbamazepine with high sensitivity at low costs and with much higher throughput than with conventional methods.

Carbamazepine and its metabolites in wastewater: Analytical pitfalls and occurrence in Germany and Portugal.

The occurrence of carbamazepine (CBZ) and its metabolites in German and Portuguese wastewater was investigated. A total of 46 samples from influent and effluent wastewater were analyzed by liquid-chromatography (LC) tandem mass spectrometry. The five metabolites 10,11-dihydro-10,11-dihydroxy-CBZ (DiOH-CBZ), 10,11-dihydro-10-hydroxy-CBZ (10-OH-CBZ), 10,11-epoxy-10,11-dihydro-CBZ, 2-hydroxy-CBZ and 3-hydroxy-CBZ were very persistent with little to no removal during wastewater treatment. The highest concentrations were found for CBZ, DiOH-CBZ, and 10-OH-CBZ, with up to 5.0, 4.8 and 1.1 µg/L, respectively. Furthermore, the related pharmaceutical oxcarbazepine and the metabolites 9-hydroxymethyl-10-carbamoylacridan, 1-hydroxy-CBZ (1-OH-CBZ) and 4-hydroxy-CBZ (4-OH-CBZ) were detected. Explicit care was taken to achieve a good chromatographic separation of the numerous isomers that were difficult to distinguish by mass spectrometry alone. A phenylether stationary phase provided the best separation. In combination with high resolution mass spectrometry and hydrogen-deuterium exchange, this LC column enabled us to identify 1-OH-CBZ and 4-OH-CBZ in wastewater for the first time.

Immunoassays as high-throughput tools: monitoring spatial and temporal variations of carbamazepine, caffeine and cetirizine in surface and wastewaters.

Carbamazepine (CBZ), caffeine and cetirizine were monitored by enzyme-linked immunosorbent assays (ELISAs) in surface and wastewaters from Berlin, Germany. This fast and cost-efficient method enabled to assess the spatial and temporal variation of these anthropogenic markers in a high-throughput screening. CBZ and cetirizine were detected by the same antibody, which selectively discriminates between both compounds depending on the pH value used in the incubation step. To our best knowledge, this is the first dual-analyte immunoassay working with a single antibody. The frequent sampling with 487 samples being processed allowed for the repeated detection of unusually high concentrations of CBZ and caffeine. ELISA results correlate well with the ones obtained by liquid chromatography tandem mass spectrometry (LC-MS/MS). Caffeine concentrations found in surface waters were elevated by combined sewer overflows after stormwater events. During the hay fever season, the concentrations of the antihistamine drug cetirizine increased in both surface and wastewaters. Caffeine was almost completely removed during wastewater treatment, while CBZ and cetirizine were found to be more persistent. The maximum concentrations of caffeine, CBZ and cetirizine found in influent wastewater by LC-MS/MS were 470, 5.0 and 0.49 µg L(-1), while in effluent wastewater the concentrations were 0.22, 4.5 and 0.51 µg L(-1), respectively. For surface waters, concentrations up to 3.3, 4.5 and 0.72 µg L(-1) were found, respectively.

Application of an ELISA to the quantification of carbamazepine in ground, surface and wastewaters and validation with LC-MS/MS.

Carbamazepine is a psychiatric pharmaceutical widely detected in aquatic environments. Due to its generalized occurrence and environmental persistence it might be considered as an anthropogenic pollution indicator. In this research, a previously developed enzyme-linked immunosorbent assay (ELISA), based on a commercial monoclonal antibody, was applied to the quantification of carbamazepine in ground, surface and wastewaters and results were validated by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The performance of the applied ELISA methodology was tested in the presence of high concentrations of sodium chloride and dissolved organic matter. The method was not significantly affected by matrix effects, being adequate for the quantification of carbamazepine in environmental samples, even without sample pre-treatment. This method allows the quantification of carbamazepine in the range of 0.03-10 µg L(-1), with a relative error lower than 30%. Due to a pH dependent cross-reactivity with cetirizine, an antihistaminic drug, the assay also enabled the quantification of cetirizine in the samples. The application of the developed method to the quantification of carbamazepine was performed by using environmental samples with very different matrices, collected in the geographical area of Ria de Aveiro, an estuarine system located in the North of Portugal. Carbamazepine was detected in all analyzed wastewater samples and in one surface water with concentrations between 0.1 and 0.7 µg L(-1). Validation with LC-MS/MS revealed that results obtained by ELISA are 2-28% overestimated, which was considered highly satisfactory due to the absence of sample pre-treatments.

Ab initio calculations for the optical rotations of conformationally flexible molecules: a case study on six-, seven-, and eight-membered fluorinated cycloalkanol esters.

Based on the time-dependent density functional response theory, an approach for the prediction of optical rotations of enantiomers of conformationally flexible molecules was developed. The method was applied successfully for the determination of the absolute configuration of trans-2-fluorocycloalkanol acetates with different ring sizes. The largest deviations between experimental and theoretical [alpha](D) values are 10 deg x [dm x (g/cc)](-1) (about 20% error). These theoretical results suggest that the optical rotation in these molecules is dominated by the local (1R;2R) configuration of the two substituents and that different ring and even axial/equatorial orientations play a less important role.