Quantitative method for conjugated metabolites of bisphenol A and bisphenol S determination in food of animal origin by Ultra High Performance Liquid Chromatography-Tandem Mass Spectrometry.

With the objectives of both generating bisphenols (BPs) conjugates occurrence data in food from animal origin but also investigating the origin of associated contamination, the present study deals with the development of an efficient analytical method aiming at monitoring both BPA and BPS conjugated metabolites in food from animal origin. The objective of such monitoring is to determine the origin of BPs contamination (FCM or animal contamination). The targeted compounds were BPA-monoglucuronide (BPA-1G), BPA-diglucuronide (BPA-2G), BPA-monosulfate (BPA-1S), BPA-disulfate (BPA-2S) and BPS-monoglucuronide (BPS-1G). The developed standard operating procedure includes a preliminary solid-liquid extraction step followed by two successive solid phase extraction (SPE) stages, using successively a non-polar phase and a strong cation exchange polymer. Quantification was achieved according to both the isotopic dilution and surrogated quantification methods, using 13C-BPA-1G and BPA-d6-1S as internal standards. Linearity was validated (R2 > 0.99) for each molecule within the concentration range [0-10] μg kg-1. Detection limits ranged from 0.02 μg kg-1 (BPA-1G in muscle, BPA-1S and BPA-2G in liver) to 0.50 μg kg-1 (BPA-2S in muscle). The strategy was then proven on liver samples collected from pregnant ewes subcutaneously exposed to BPA during 105 days, at 50 μg kg-1 per day. BPA-1G, BPA-2G and BPA-1S were detected and quantified at a concentration of 3.81 μg kg-1, 0.80 μg kg-1 and 0.09 μg kg-1, respectively. The analytical method was finally implemented on fifty unpacked food samples from animal origin in which significant free BPA concentrations were previously measured. Since no metabolites of BPA could be measured (<LOD), it means that such free BPA present in the samples originates from direct contact of the food item with a material containing BPA.