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

Document Type : Research Paper




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