Simultaneous quantification of bisphenol A and its glucuronide metabolite (BPA-G) in plasma and urine: applicability to toxicokinetic investigations.

Bisphenol A (BPA) is a widely used plasticizer that can contaminate food and the wider environment and lead to human exposure. In humans, it is mainly metabolized to bisphenol A-glucuronide (BPA-G) and eliminated in the urine. As BPA causes adverse physiological effects at low doses, it is necessary to document the toxicokinetics of both molecules for risk assessment. Because BPA-G is not available as an analytical standard, it is usually quantified after the assay of BPA, following an enzymatic hydrolysis with β-glucuronidase. With this approach, two separate assays are required for BPA and BPA-G quantification, which can lead to critical pitfalls in terms of accuracy and analysis time. To overcome this problem, we have developed a new method for the isolation and purification of BPA-G from urine by flash chromatography. Large amounts of BPA-G (1g) were isolated and characterized by mass spectrometry and NMR. This BPA-G is suitable for an use as analytical standard and enabled us to develop a novel method for the simultaneous quantification of BPA and BPA-G in biological matrices by UPLC/MS/MS. It has also been used for in vivo toxicokinetic studies in sheep. The method of quantification was validated according FDA guidelines and used to monitor the time course of plasma and urine concentrations of BPA or BPA-G following their administration. The simultaneous quantification of BPA and BPA-G was compared to the commonly used method for urine and plasma samples. For plasma samples, the results obtained with the direct assay of BPA-G were similar to those obtained by quantification after enzymatic hydrolysis. With urine samples, the simultaneous quantification appeared to be more suitable than the hydrolysis method for the BPA-G determination.