Factors Affecting the Accuracy of Bisphenol A and Bisphenol A-Monoglucuronide Estimates in Mammalian Tissues and Urine Samples

ABSTRACTBisphenol A (BPA) (CAS Number 80–05-7; EINECS Number 201–245-8) is used in the production of plastics having food contact applications. Some biomonitoring studies have reported free BPA in blood or urine of humans. Since complete first-pass metabolism of orally administered BPA to BPA-monoglucuronide (BPA-G) occurs in humans, the presence of free BPA in human specimens raises questions as to the origin and/or possible sources of the free BPA. We hypothesized that BPA-G instability during specimen collection and analysis contributes to the presence of free BPA in the biological samples. Investigation of the in vitro hydrolysis of BPA-G in blood plasma, tissue homogenates, and diluted urine from laboratory rats and in aqueous/organic solutions commonly used for extraction in BPA analyses lent support to the hypothesis of BPA-G instability as a possible source of free BPA determinations in the biological specimens. Hydrolysis of BPA-G occurred at neutral pH and room temperature in diluted urine and i...