Matrix solid-phase dispersion extraction of organophosphorus pesticide using SiO₂-poly(N-vinylimidazole)

A sorbent material based on silica particles modified with poly(N-vinylimidazole) (SiO₂-PVI) has been evaluated for the treatment of samples by matrix solid-phase dispersion (MSPD). The extraction of four organophosphorus pesticides was done from a spiked tomato and the extracts were analyzed by gas chromatography coupled to mass spectrometry. Six elution solvents were evaluated and acetone was selected due to better recovery of the four pesticides and low background signal in the chromatograms. A factorial design 2⁴ was used for selection of extraction conditions. The factors were contact time, acetone volume, treatment (with or without freeze-drying) and adsorbent (SiO₂ or SiO₂-PVI). The best recoveries were obtained using 15 minutes of contact, 2 mL of solvent and sorbent without freeze-drying. The recoveries were between 60 and 83% for SiO₂-PVI in spiked tomato with 0.2 and 0.8μg/g.