Determination of bisphenol A and bisphenol S in sacked mouse foods by liquid chromatography-tandem mass spectrometry

Numerous studies suggested that exposure to endocrine disrupting chemicals (EDCs) such as bisphenol A (BPA) and bisphenol S (BPS) at low dose might induce various toxicity in animals. However, contamination of BPA and BPS in animal foods used in animal experiments and the effect of EDCs exposure to the animals were seldom investigated. Herein, an analytical method using liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) was applied for the analysis of BPA and BPS in mouse foods. The analytes were identified by using Orbitrap MS/MS in negative ionization mode and quantified by triple quadrupole tandem mass spectrometer in multiple reaction monitoring (MRM) mode. BPA and BPS were extracted from mouse foods with acetonitrile. The extract was cleaned-up using a hydrophilic lipophilic balanced (HLB) solid-phase extraction cartridge. The method had good recovery (85.6%–94.5%), low limits of quantification (1 ng/g for BPA and 0.2 ng/g for BPS), good linearity of calibration (R² = 0.999), and acceptable inter/intra-precision (2.2%–8.5%). The method was successfully applied to analyze eight mouse food samples. The average concentrations of BPA and BPS in the food were 124.71 and 1.08 ng/g, respectively. For an adult mouse with the body weight (BW) of 25 g and with a daily food intake of 4 g, the BPA intake from food would be 19.95 μg/kg BW/day, which is higher than the low exposure dosages of BPA mentioned in many previous studies. Therefore, the obtained results from this study showed the importance of determining the contaminants like BPA and BPS in mouse foods before planning their pharmacokinetic or toxicologic studies.