Gel filtration clean-up for multi-residues of organophosphorus pesticides in rice

Gel filtration on Bio-Beads S-X8 and Sephadex LH-20 columns has been successfully applied to the clean-up of multiple residues of malathion, fenitrothion and dichlorvos in rice. Recoveries were checked by gas-liquid chromatography using CsBr-thermionic detector and ranged from 77 to 104% at 5 mg/kg level. The clean-up was found to be highly effective. No interference was observed in the gas chromatograms.