Multiresidue method for the analysis of pesticide residues in leafy vegetables by supercritical fluid extraction and capilary gas chromatography

The applicability of supercritical fluid extraction (SFE) in organophosphorus pesticide multi-residue analysis in vegetable samples was investigated. Fortification experiment and orthogonal test based on the trichlorfon as investigating target were conducted to optimize the extraction procedure in SFE by varying the CO₂ flow, extraction oven temperature, outlet temperature and pressure. The best efficiency was achieved at 18mL·min^-1, 60°C, 80°C and 350 bar, respectively. The analytical screening was performed by capillary gas chromatography equipped with flame photometric detector (FPD). Recoveries for the majority of pesticides from spiked samples of vegetable with the fortification level of 0.04-0.10 mg·kg^-1 ranged from 80.5 to 97.3%, and the relative standard deviation (RSD) was from 2.9 to 8.4. The detection limits were from 0.008 to 0.035 mg·kg^-1 for FPD, and meeting the requirement set of native standard. The optimized SFE method is a simple,low cost, environment-friendly and an effective preparation method for determination of pesticide multi-residue at trace level in leafy vegetables in comparison with solid-liquid extraction method.