Application of Eutectic-Solvent-Based Liquid–Liquid Microextraction for Removal of Eight Bisphenols from Water and Industrial Samples

In this study, new types of eutectic solvents (ESs) are tested for their ability to remove the eight most common bisphenols (BPA, BPB, BPC, BPE, BPF, BPG, BPS, BPAP), which are environmentally monitored substances, from aqueous matrices. A total of 18 ESs based on hydrophobic organic acids, such as capric, caprylic, lauric, and myristic acids, and terpenes, such as DL-menthol, terpineol, linalool, and geraniol, are prepared and mixed in various molar ratios. The highest extraction yield for all types of BPs is achieved with a binary mixture of geraniol:caprylic acid prepared in a molar ratio of 1:1. This ES can be used repeatedly for five consecutive cycles achieving almost 100% recovery for BPB, BPC, BPG, and BPAP, while for BPA, BPE, and BPF, the yield drops to 97% and for BPS to 90%. The efficiency of ES extraction is verified using HPLC-MS/MS to determine the BPs in the aqueous phase. This is performed at a pentafluorophenylpropyl stationary phase with LOQs ranging from 0.24 to 29.1 ng/mL. The applicability of this HPLC-MS/MS method was demonstrated by monitoring the occurrence of BPs in thermal paper and other industrial samples.