Determination of Per- and Polyfluoroalkyl Substances in Vegetables by Solid-Phase Extraction Combined with Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry
Vegetable consumption is a well-established pathway for human exposure to per- and polyfluoroalkyl substances (PFAS). These contaminants are absorbed by vegetables through uptake from soil and irrigation water, leading to bioaccumulation within plant tissues and posing potential risks to human health. Therefore, monitoring PFAS concentrations in vegetables is critical for assessing dietary exposure and associated health risks. In this study, a solid-phase extraction (SPE) followed by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed for the determination of 24 PFAS compounds in leafy vegetables, including Shanghai Bok Choy, Cabbage, and Water Spinach. The analytical method, incorporating organic solvent extraction followed by SPE cleanup, was optimized with respect to both extraction solvent and SPE sorbent. Alkaline methanol was used as the extraction solvent, and PFAS in vegetables were extracted via vortex-assisted extraction. Tandem mass spectrometry was used for detection in multiple reaction monitoring mode, and quantification was performed by internal standard method. Under optimized conditions, at a spiking level of 2 ng, recoveries ranged from 50.0% to 120.8% with relative standard deviations (RSD) between 1.0% and 26%. Calibration curves showed good linearity with correlation coefficients (r) greater than 0.99. Limits of detection (LOD, S/N=3) were between 0.002 and 0.103 ng·g−1, and limits of quantification (LOQ, S/N=10) were between 0.007 and 0.343 ng·g−1. The method was applied to real samples, detecting 20 PFAS, with 10 compounds showing 100% detection frequency. Total PFAS concentrations ranged from 2.92 to 6.83 ng·g−1 dry weight (dw). Perfluorobutanoic acid (PFBA) was the dominant contaminant, with concentrations from 1.18 to 3.74 ng·g−1 dw. The method demonstrates good sensitivity and accuracy, effectively identifying and quantifying multiple PFAS, thus providing reliable technical support for monitoring PFAS in vegetables.