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The extensive use of bisphenol A (BPA) in the manufacture of consumer products results in widespread human exposure to the chemical. In the body, BPA undergoes first-pass metabolism to form BPA glucuronide, considered to be a major BPA byproduct. Concentrations of total (free plus conjugated) urinary species of BPA are used to assess human exposure to BPA. However, because BPA can be present in numerous consumer and household products, potential contamination with parent BPA during collection and handling may pose a challenge when measuring BPA in such biological samples as blood or urine. In this study we investigated the in-vitro phase I metabolism of BPA in rat and human liver microsomes by using on-line solid-phase extraction-high-performance liquid chromatography-tandem mass spectrometry to identify phase I metabolites (e.g., BPA oxidation products) that could be used as potential alternative biomarkers of BPA exposure. We unambiguously identified 5-hydroxy BPA (BPA catechol) as an in-vitro oxidative metabolite of BPA, but human microsomes oxidized only about 10% of BPA to BPA catechol. We evaluated the usefulness of BPA catechol as a potential biomarker of human exposure to BPA by measuring total concentrations of BPA catechol and BPA in 20 urine samples. We detected BPA catechol at much lower concentrations and frequency than those of BPA. Furthermore, we found that free BPA catechol was rather unstable in urine, which highlights the importance of sampling techniques to adequate interpretation of biomonitoring data. Together, these findings suggest that BPA catechol may not be a suitable biomarker of environmental exposure to BPA, but could be used to confirm BPA exposure in special populations or in situations when urine specimens were potentially contaminated with BPA. [ABSTRACT FROM AUTHOR]

The free and conjugated urinary species of non-persistent environmental chemicals or their breakdown products are valid human exposure biomarkers. For convenience, disposable diapers and other absorbent materials are widely used to collect urine specimens from infants and young toddlers. However, the extent to which the different urinary species of the target analytes and other components are recovered after the urine is extracted from these absorbent materials is unknown. In this proof-of-concept study, we investigated the extraction recovery from disposable diapers, cotton pads, and gauzes of the free versus glucuronidated urinary species of three example chemicals: bisphenol A, triclosan, and 4-methylumbelliferone. Although the glucuronides were almost fully recovered, the free species were not. Our results suggest that, in addition to other sampling considerations, the binding affinity and extraction recovery of the target biomarkers to the material used to collect the urine should be considered. Alternative collection approaches that do not require such an extraction (e.g., urine bags routinely used in hospitals) may be worth exploring. Despite its shortcomings, having urinary concentrations for biomonitoring considerably strengthens the exposure assessment, particularly for infants and young toddlers, and the benefits of including biomonitoring data outweigh their potential limitations. [ABSTRACT FROM AUTHOR]

Abstract  The infrared spectrum of ether was studied using Fourier transform infrared spectroscopy in conjunction with the density functional theory (DFT). The optimized structures and vibrational frequencies of the ether·(H2O) n (n = 1–3) complexes were obtained at B3LYP/6-31G(d) theory levels. Compared to those of free-form ether, the C–O stretching vibrational frequencies of the ether–water complexes are found to shift to red by up to 39 cm−1 with an increase in the C–O length of 0.016 Å. Meanwhile, the frequency of the O–H stretching modes of water in the complexes appears significantly redshifted to a varying degree. The DFT calculations suggest that these shifts are caused by the hydrogen bonding between ether and water. [ABSTRACT FROM AUTHOR]