Multiresidue determination of organophosphorus pesticides in corn oil using solid-phase extraction with lanthanum silicate sorbent and gas chromatography

Abstract

Phosalone, malathion and diazinon were analyzed in corn oil using solid phase extraction (SPE)<br />with lanthanum silicate as a new solid sorbent followed by gas chromatography with nitrogen<br />phosphorus detection (GC-NPD). The efficiency of different eluents (methanol, dichloromethane,<br />ethyl acetate, dichloromethane — ethyl acetate (1:1) and ethyl acetate — methanol (1:1)) were<br />compared for elution of organo-phosphorus pesticides on lanthanum silicate-SPE in corn oil.<br />Recoveries with methanol as eluent were 87% for phosalone, 95% for malathion and 69% for<br />diazinon with standard deviations of 5-14% in the concentration range of 0.5-2 mg kg-1. The<br />limits of detection for these organophosphorus pesticides, were lower than maximum residue<br />limits (MRLs) established by WHO/FAO. Thin layer chromatography was performed using bed<br />of lanthanum silicate ion exchanger to ensure the existence of the pesticides residue in the SPEextract.<br />They were determined using gas chromatograph equipped with nitrogen phosphorus<br />detector.