Challenges in the Analyses of Organophosphate Esters

Organophosphate esters (OPEs) have been subject to considerable scientific and public scrutiny in recent years. The combination of their physicochemical characteristics and lack of standard analytical methods has resulted in growing concerns with respect to the validity of OPE concentrations reported in the literature. The goal of this study was to address the analytical challenges in analyses of OPEs by comparing the precision and accuracy of data generated for individual target analytes by different laboratories. Eleven international research laboratories were recruited in this study, and a total of 16 OPEs, chosen among the most frequently reported ones, were targeted. Results demonstrate the participating laboratories had generally good to very good consistency for the suite of OPEs analyzed, but accuracy was found to be a problem for several OPEs and laboratories. Methods utilized for the quantification of tri-<i>m</i>-tolyl phosphate, tri-<i>p</i>-tolyl phosphate, and tris­(2-butoxyethyl) phosphate performed worst overall, as highlighted by their zeta-scores, suggesting that interpretation and comparison of results for these OPEs should be made with caution and that current analytical methods may need to be improved. Liquid chromatography and tandem mass spectrometry performed best for both precision and accuracy

Enantioselective Analytical- and Preparative-Scale Separation of Hexabromocyclododecane Stereoisomers Using Packed Column Supercritical Fluid Chromatography

Hexabromocyclododecane (HBCDD) is an additive brominated flame retardant which has been listed in Annex A of the Stockholm Convention for elimination of production and use. It has been reported to persist in the environment and has the potential for enantiomer-specific degradation, accumulation, or both, making enantioselective analyses increasingly important. The six main stereoisomers of technical HBCDD (i.e., the (+) and (−) enantiomers of α-, β-, and γ-HBCDD) were separated and isolated for the first time using enantioselective packed column supercritical fluid chromatography (pSFC) separation methods on a preparative scale. Characterization was completed using published chiral liquid chromatography (LC) methods and elution profiles, as well as X-ray crystallography, and the isolated fractions were definitively identified. Additionally, the resolution of the enantiomers, along with two minor components of the technical product (δ- and ε-HBCDD), was investigated on an analytical scale using both LC and pSFC separation techniques, and changes in elution order were highlighted. Baseline separation of all HBCDD enantiomers was achieved by pSFC on an analytical scale using a cellulose-based column. The described method emphasizes the potential associated with pSFC as a green method of isolating and analyzing environmental contaminants of concern.publishedVersio

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49 50 51 52 53 54 55 56 57 58 59 60 Section: Original Research Articles. Research Area: Systems Toxicology o,p&apos;-DDT elicits PXR/CAR, not ER, mediated responses in the immature, ovariectomized rat live

Release of PCDD/PCDF to air and land during open burning of sugarcane and forest litter over soil fortified with mass labelled PCDD/PCDF

The contribution of PCDD/PCDF emissions from soil during open burning of biomass was examined. Mass labelled PCDD/PCDF was added to soil containing native PCDD/PCDF and biomass was laid out on this soil and burnt, simulating sugarcane trash and forest fires. Smoke samples were collected using a high volume portable field sampler. After each fire the concentration of all mass labelled PCDD/PCDF congeners in the surface soil decreased, however, the concentration of some native 2,3,7,8 substituted congeners increased, indicating that formation was occurring. Mass labelled PCDD/PCDF congeners were detected in all ash samples, mean 2.8 pg g(-1) (range 0.5-8 pg g(-1)), demonstrating release from the soil. Additionally, mass labelled PCDD/PCDF congeners were detected in all air samples mean 1.2 mu g (t fuel)(-1) (range 0.2-2.0 mu g (t fuel)(-1)), again demonstrating release from the soil. Native 2,3,7,8 substituted congeners detected in the air samples were dominated (in terms of contribution to total congener mass) by Cl8DD (90% for forest litter and 77% for sugarcane). The major contributor to TEQ of emissions from both forest litter and sugarcane was 1, 2, 3, 7, 8-Cl5DD (40-64% and 57-75%, respectively). These results demonstrate that release of PCDD/PCDF from soil to air and land occurs during open burning of biomass when soil temperatures are sufficiently elevated. (C) 2012 Elsevier Ltd. All rights reserved

Release of native and mass labelled PCDD/PCDF from soil heated to simulate bushfires

Soil is an important reservoir of PCDD/PCDF, which can be released when environmental conditions change. Fire is an extreme event that can increase the surface temperatures of soil substantially, yet little is known of the role soil plays in the emission of PCDD/PCDF. Soil containing native PCDD/PCDF was fortified with a mixture of mass labelled PCDD/PCDF and heated between 150 degrees C and 400 degrees C. Both native and mass labelled PCDD/PCDF were released from the soil beyond 200 degrees C. Release of the mass labelled compounds was linearly related to temperature with up to 9% found in the air stream at 400 degrees C. The release of some native PCDD/PCDF was much greater. At 400 degrees C, emission of 1,2,3,7,8-Cl5DD was 300% compared to pre-experimental soil. Emission of PCDD/PCDF from soil during bushfires is a relevant process and may originate from both volatilization and formation via de novo or precursor pathways, or dechlorination. (C) 2012 Elsevier Ltd. All rights reserved

Species-Specific Regulation of PXR/CAR/ER-Target Genes in the Mouse and Rat Liver Elicited by o,p'-DDT

BACKGROUND: Dichlorodiphenyltrichloroethane (DDT) is a persistent estrogenic organochlorine pesticide that is a rodent hepatic tumor promoter, with inconclusive carcinogenicity in humans. We have previously reported that o, p'-DDT elicits primarily PXR/CAR-mediated activity, rather than ER-mediated hepatic responses, and suggested that CAR-mediated effects, as opposed to ER-mediated effects, may be more important in tumor promotion in the rat liver. To further characterize species-specific hepatic responses, gene expression analysis, with complementary histopathology and tissue level analyses were investigated in immature, ovariectomized C57BL/6 mice treated with 300 mg/kg o, p'-DDT, and compared to Sprague-Dawley rat data. RESULTS: Rats and mice exhibited negligible histopathology with rapid o, p'-DDT metabolism. Gene expression profiles were also similar, exhibiting PXR/CAR regulation with the characteristic induction of Cyp2b10 and Cyp3a11. However, PXR-specific target genes such as Apoa4 or Insig2 exhibited more pronounced induction compared to CAR-specific genes in the mouse. In addition, mouse Car mRNA levels decreased, possibly contributing to the preferential activation of mouse PXR. ER-regulated genes Cyp17a1 and Cyp7b1 were also induced, suggesting o, p'-DDT also elicits ER-mediated gene expression in the mouse, while ER-mediated effects were negligible in the rat, possibly due to the inhibitory effects of CAR on ER activities. In addition, o, p'-DDT induced Gadd45a, Gadd45b and Cdkn1, suggesting DNA damage may be an additional risk factor. Furthermore, elevated blood DHEA-S levels at 12 h after treatment in the mouse may also contribute to the endocrine-related effects of o, p'-DDT. CONCLUSION: Although DDT is known to cause rodent hepatic tumors, the marked species differences in PXR/CAR structure, expression patterns and ligand preference as well as significant species-specific differences in steroidogenesis, especially CYP17A1 expression and activity, confound the extrapolation of these results to humans. Nevertheless, the identification of potential modes of action as well as species-specific responses may assist in the selection and further development of more appropriate models for assessing the toxicity of DDT to humans and wildlife