Automated miniaturized LLE-GC-MS/MS for the analysis of EPA 8270 SVOCs and multi-class pesticides in water using ethyl acetate.

The determination of trace-level semi-volatile organic compounds (SVOCs) following EPA Method 8270 traditionally relies on manual liquid-liquid extraction (LLE) using large volumes of dichloromethane (DCM). However, recent 2024 TSCA regulations restricting DCM due to human health risks necessitate sustainable analytical alternatives. This study presents a fully automated, miniaturized LLE (micro-LLE) method for 170 analytes including EPA 8270 targets and multi-class pesticides (organochlorine (OCPs), organophosphorus (OPPs) and organonitrogen (ONPs) pesticides and pyrethroids). The workflow utilizes a TriPlus RSH SMART autosampler to integrate standard preparation, surrogate spiking, and extraction with on-line GC-MS/MS injection. Ethyl acetate was validated as a "green" alternative to DCM, with a 1:1 NaCl:MgSO₄ salt mixture optimizing the salting-out effect. This procedure achieved a tenfold enrichment factor using only 1.5 mL of solvent for 10 mL of sample. Method validation showed excellent linearity (R2> 0.995 for 70% of analytes) and precision (RSD < 15%). Method limits of quantification (MLOQs) between 0.05 and 10 µg/L meet stringent regulatory requirements. The method's robustness was confirmed through real-world Saharan deposition samples, identifying high levels of Phenothrin (211 ppb) and Endosulfan ether (140 ppb). This robotic workflow provides a high-throughput, sustainable solution for modern environmental monitoring.