QuEChERS-Based Extraction Procedures for the Analysis of Bisphenols S and A in Breast Milk Samples by LC-QqQ-MS

Different extraction and clean-up protocols, based on either the dispersive solid-phase extraction (d-SPE) and the quick, easy, cheap, effective, rugged, and safe (QuEChERS) approach, were optimized and compared for the determination of selected bisphenols such as bisphenol A (BPA) and bisphenol S (BPS) in breast milk samples. QuEChERS-based sample preparation procedure was optimized by evaluation of different clean-up sorbents including zirconium-based sorbents (Z-Sep and Z-Sep Plus) and primary secondary amine. Negligible matrix interference was observed for most of the analytes due to application of 45 mg Z-Sep or 45 mg Z-Sep + 5 mg Z-Sep Plus sorbents in d-SPE clean-up step. Acceptable analytical performance for the BPA and BPS was observed with recoveries percentage in the range of 70-92% and RSD less than 15%. The pilot study was performed by applying HPLC with diode-array detection, and optimized procedures were transferred to the LC triple-quadrupole MS system. LC with electrospray ionization and tandem MS operating in the multiple reaction monitoring mode provide high sensitivity and selectivity for trace analysis. The LODs were 0.10 and 0.54 ng/mL, and the LOQs were 0.20 and 1.35 ng/mL for BPS and BPA, respectively. The developed procedures were evaluated in terms for material collection obtained from women (inhabitants of Lublin, Poland). In 20 samples, bisphenol residues were detected at concentrations from 0.09 to 11.56 ng/mL.