Multicolumn solid-phase extraction cleanup of organophosphorus and organochlorine pesticide residues in vegetable oils and butterfat.

Diatomaceous earth columns used with reversed and normal solid phase extraction (SPE) cartridges were evaluated for the quantitative determination of a number of organophosphorus (OP) and organochlorine (OC) pesticide residues in edible vegetable oils and butterfat. An oil or fat sample (about 2 g) in hexane was passed through a diatomaceous earth (Extrelut QE) column and a C18 bonded silica (ODS) SPE cartridge, resulting in the separation of the pesticides from about 98% of the lipids. The eluate was split in half, with the first portion concentrated into acetone for the determination of OP pesticides by gas chromatography with flame photometric detection (GC-FPD). The other half was passed through an Alumina-N SPE cartridge for additional cleanup of lipid matrix to determine OC pesticides by GC with electron-capture detection (GC-ECD). Average recoveries from fortified samples were greater than 89% for the pesticides studied.