Single-step multi-cartridge clean-up for organophosphate pesticide residue determination in vegetable oil extracts by gas chromatography.

A multi-cartridge system has been developed which, in a single step, performs the extraction and clean-up of organophosphate (OP) pesticide residues from oils and fatty extracts. A solution in hexane containing up to 1.8 g of lipidic material is loaded on to an Extrelut-3 column to which a silica-gel cartridge and a C18 silica cartridge have been connected in series. The OP pesticide residues are eluted with 15 ml of acetonitrile. Carry-over of fatty material is in the range 2-5 mg per 1.8 g of different oils, which makes the final solution amenable to capillary gas chromatography. Recoveries of 23 OP pesticides were in the range 82-111%. The whole procedure takes ca. 20 min and compares favourably with current procedures.