Sensitive and Rapid Determination of Long-Chain Per- and Polyfluoroalkyl Substances in Milk Using Fe3O4-PSA-Based Magnetic Solid-Phase Extraction Coupled with LC-MS/MS

A sensitive and time-saving method was developed for the determination of 11 long-chain per- and polyfluoroalkyl substances (PFASs) in milk using magnetic solid phase extraction (MSPE) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). A primary–secondary amine-modified Fe3O4 (Fe3O4-PSA) sorbent was used for the extraction and enrichment of PFASs from milk. The adsorption behavior of PFASs on Fe3O4-PSA was investigated, and the experimental results suggest the involvement of electrostatic and hydrophobic interactions. Effects of sample solution pH, adsorbent amount, adsorption time, eluting solvent type, and elution time on the recovery of PFASs were investigated, and the optimal conditions were determined. The results show that the method exhibited good linearity (R2 > 0.9972) in the range of 0.005–20 μg/kg. The limit of detection (LOD) ranged from 0.008–0.062 μg/kg, and the limit of quantitation (LOQ) ranged from 0.0260–0.206 μg/kg. Recoveries of the 11 PFASs in spiked milk samples (0.5, 5, and 20 μg/kg) ranged from 79.4% to 118% with RSDs below 17%. Therefore, the developed method demonstrated potential for the determination of PFASs in milk samples.