Development of a Method for the Determination of Bisphenol A at Trace Concentrations in Human Blood and Urine and Elucidation of Factors Influencing Method Accuracy and Sensitivity

Abstract

Bisphenol A (BPA) is an industrial chemical used to make polymers including some used in food contact applications. Virtually complete presystemic clearance of orally administered BPA occurs in humans by metabolism to BPA-glucuronide (BPA-G), but some biomonitoring studies report low concentrations of free (parent) BPA in human blood and urine. Trace contamination of BPA from exogenous sources or hydrolysis of BPA-G to free BPA, either during or after biomonitoring specimen collection, may have contributed to the reported concentrations of free BPA. An analytical method for the determination of free BPA in human blood and urine was developed and validated in two independent laboratories, using the latest generation of high-performance liquid chromatography-tandem mass spectrometry instrumentation to ensure the desired high sensitivity and selectivity. The method was designed to account for and/or eliminate background contamination from all sources and demonstrated that contamination could occur from devices used for specimen collection or storage, as well as other sources. The method employed an internal standard (BPA-d(8)) and demonstrated accuracy and reproducibility in both matrices fortified with BPA or a surrogate analyte ((13)C-BPA) at a low quantitation limit (0.1-0.2 ng/mL). For validation, five replicate samples were analyzed to evaluate reproducibility. Importantly, it was demonstrated that the conditions of the method did not result in the hydrolysis of BPA-G to free BPA, another possible source of error in BPA analysis. Application of the principles defined by this method will be critical to assure valid analytical results in any future biomonitoring studies.

Bisphenol A and the risk of cardiometabolic disorders: a systematic review with meta-analysis of the epidemiological evidence

“…Less expensive methods have been proposed, focusing on BPA metabolites (e.g., BPA-glucuronide) [70, 71]. It has been suggested that part of the BPA measured in human samples can be due to contamination during sample collection or laboratory measurements [72, 73], and one of the great advantages of studying BPA metabolites is to avoid these contamination issues. The lower cost of these methods would also allow measuring BPA in larger populations.…”

Evidence that bisphenol A (BPA) can be accurately measured without contamination in human serum and urine, and that BPA causes numerous hazards from multiple routes of exposure

“…The potential for assay contamination is thus not unique to BPA, and simply requires the use of standard assay procedures and appropriate controls that should be routinely employed, which has also been the conclusion reached by others (Calafat and Needham, 2009; Markham et al, 2010; Vandenberg et al, 2014a). It is important to note that the two groups of scientists that have promoted the belief that BPA cannot be assayed in human serum without contamination, the FDA laboratory (Doerge et al, 2010a; Churchwell et al, 2014), and a plastic-industry funded laboratory (Dekant and Volkel, 2008; Volkel et al, 2002), are the two laboratories that in their publications have reported uncontrolled contamination and high background BPA in their assays.…”

“…Given this statement as a pillar for their argument that biologically active serum levels of unconjugated BPA reported in numerous studies can be ignored, along with the fact that it is contradicted by data we have presented earlier and inconsistent with standard analytic laboratory procedures, it is crucial to identify what exactly was stated in the eight studies Patterson et al (2013) cited as support for their statement (the articles cited were: Doerge et al, 2012; Koch et al, 2012; Markham et al, 2010; Salgueiro-Gonzalez et al, 2012; Teeguarden et al, 2011; Twaddle et al, 2010; Vandentorren et al, 2011; Volkel et al, 2002). In fact, examination of these publications reveals that the Patterson et al (2013) statement is not consistent with the conclusions drawn by most of the authors that they cite.…”

“…As correctly noted in a chemical-industry study, adequate control of contamination is required in order to publish results if analysis of human serum and urine levels are to be believed (Markham et al, 2010). Supporting the contention that BPA contamination can be controlled in human biomonitoring studies is a report from the CDC in which sources of contamination were identified and systematically eliminated during the successful development of LC–MS/MS assays for BPA and three other chemicals (Ye et al, 2013).…”

“…Second, the objective of the Markham et al (2010) study was “to account for and/or eliminate background contamination from all sources.” Markham et al reported on a comparison of BPA serum and urine assay performance in two laboratories, and they reported very good accuracy and precision, although this was reduced at the very lowest dose examined compared to higher doses, consistent with typical assay performance. Third, Salgueiro-Gonzalez et al (2012) conducted an analysis of sources of blank contamination in BPA, as well as nonylphenol and octylphenol, assays and concluded that: “the main contamination sources in DLLME–LC–MS/MS were considered and >90% of the contamination could be removed by following the guidelines described here”.…”