title: A round robin approach to the analysis of bisphenol A (BPA) in human blood samples.
abstract: BACKGROUND
  Human exposure to bisphenol A (BPA) is ubiquitous, yet there are concerns about whether BPA can be measured in human blood. This Round Robin was designed to address this concern through three goals: 1) to identify collection materials, reagents and detection apparatuses that do not contribute BPA to serum; 2) to identify sensitive and precise methods to accurately measure unconjugated BPA (uBPA) and BPA-glucuronide (BPA-G), a metabolite, in serum; and 3) to evaluate whether inadvertent hydrolysis of BPA-G occurs during sample handling and processing.
  
  
  METHODS
  Four laboratories participated in this Round Robin. Laboratories screened materials to identify BPA contamination in collection and analysis materials. Serum was spiked with concentrations of uBPA and/or BPA-G ranging from 0.09-19.5 (uBPA) and 0.5-32 (BPA-G) ng/mL. Additional samples were preserved unspiked as 'environmental' samples. Blinded samples were provided to laboratories that used LC/MSMS to simultaneously quantify uBPA and BPA-G. To determine whether inadvertent hydrolysis of BPA metabolites occurred, samples spiked with only BPA-G were analyzed for the presence of uBPA. Finally, three laboratories compared direct and indirect methods of quantifying BPA-G.
  
  
  RESULTS
  We identified collection materials and reagents that did not introduce BPA contamination. In the blinded spiked sample analysis, all laboratories were able to distinguish low from high values of uBPA and BPA-G, for the whole spiked sample range and for those samples spiked with the three lowest concentrations (0.5-3.1 ng/ml). By completion of the Round Robin, three laboratories had verified methods for the analysis of uBPA and two verified for the analysis of BPA-G (verification determined by: 4 of 5 samples within 20% of spiked concentrations). In the analysis of BPA-G only spiked samples, all laboratories reported BPA-G was the majority of BPA detected (92.2 - 100%). Finally, laboratories were more likely to be verified using direct methods than indirect ones using enzymatic hydrolysis.
  
  
  CONCLUSIONS
  Sensitive and accurate methods for the direct quantification of uBPA and BPA-G were developed in multiple laboratories and can be used for the analysis of human serum samples. BPA contamination can be controlled during sample collection and inadvertent hydrolysis of BPA conjugates can be avoided during sample handling.
authors.forename: Laura N
authors.initials: LN
authors.lastname: Vandenberg
authors.forename: Roy R
authors.initials: RR
authors.lastname: Gerona
authors.forename: Kurunthachalam
authors.initials: K
authors.lastname: Kannan
authors.forename: Julia A
authors.initials: JA
authors.lastname: Taylor
authors.forename: Richard B
authors.initials: RB
authors.lastname: van Breemen
authors.forename: Carrie A
authors.initials: CA
authors.lastname: Dickenson
authors.forename: Chunyang
authors.initials: C
authors.lastname: Liao
authors.forename: Yang
authors.initials: Y
authors.lastname: Yuan
authors.forename: Retha R
authors.initials: RR
authors.lastname: Newbold
authors.forename: Vasantha
authors.initials: V
authors.lastname: Padmanabhan
authors.forename: Frederick S
authors.initials: FS
authors.lastname: Vom Saal
authors.affiliation: Program on Reproductive Health and the Environment, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California - San Francisco, San Francisco, CA, USA. woodrufft@obgyn.ucsf.edu.
authors.forename: Tracey J
authors.initials: TJ
authors.lastname: Woodruff
mesh_terms: D000818:Animals; D001559:Benzhydryl Compounds / Q000097:blood*; D001800:Blood Specimen Collection / Q000379:methods; D002851:Chromatography, High Pressure Liquid; D004784:Environmental Monitoring; D004785:Environmental Pollutants / Q000097:blood*; D020719:Glucuronides / Q000097:blood; D006801:Humans; D007753:Laboratories; D010636:Phenols / Q000097:blood*; D051381:Rats; D053719:Tandem Mass Spectrometry; D000098826:Bisphenol A Compounds
chemical_list: D001559:Benzhydryl Compounds; D004785:Environmental Pollutants; D020719:Glucuronides; D010636:Phenols; C512161:bisphenol A glucuronide; D000098826:Bisphenol A Compounds; C006780:bisphenol A