RSM-optimized automated DI-SPME-GC-MS/MS for multi-class trace plasticizers in drinking water

The simultaneous determination of multiple plasticizers in drinking water remains challenging because of their trace concentrations, diverse physicochemical properties, and susceptibility to background contamination. In this study, an automated direct immersion solid-phase microextraction (DI-SPME) method coupled with gas chromatography-triple quadrupole tandem mass spectrometry (GC-MS/MS) was developed for the simultaneous determination of 29 plasticizers from four classes in drinking water, including 17 phthalate esters (PAEs) and 12 non-phthalate plasticizers (NPPs). Cost-effective internal standards were employed for quantification. A 120 µm divinylbenzene/carbon wide range/polydimethylsiloxane (DVB/Carbon WR/PDMS) SPME Arrow exhibited the most balanced extraction performance for the target analytes. Extraction parameters were optimized via a sequential response surface methodology (RSM) strategy considering potential factor interactions. Under the optimized conditions (extraction temperature 66 °C, extraction time 34 min, and desorption time 336 s), the method showed linear dynamic ranges (LDRs) of 0.005-20 µg L^-1 with coefficients of determination (R²) ≥ 0.9907 for all analytes. The limits of detection (LODs) ranged from 0.002 to 0.02 µg L^-1, and the limits of quantification (LOQs) ranged from 0.005 to 0.05 µg L^-1. Recoveries at three spiked levels (0.05, 0.5, and 5 µg L^-1) ranged from 82.24% to 119.07%, with relative standard deviations (RSDs) of 1.71-10.89%. Application to 18 end-use and 12 bottled drinking water samples showed total plasticizer concentrations ranging from 1.33 to 19.5 µg L^-1 (median: 4.87 µg L^-1) and from 1.46 to 11.2 µg L^-1 (median: 5.47 µg L^-1), with up to 14 analytes simultaneously detected in a single sample. DEHP (di(2-ethylhexyl) phthalate) showed the highest median concentration among the detected plasticizers, followed by DBP (dibutyl phthalate), while end-use water exhibited greater diversity of plasticizer species than bottled water. Greenness and sustainability assessment using multiple complementary tools demonstrated favorable sustainability characteristics of the proposed method. With broad analyte coverage, automated operation, and negligible matrix effects, the proposed method provides a practical and sensitive platform for comprehensive plasticizer monitoring in drinking water.