Evaluation of a solid phase extraction procedure for the determination of pesticide residues in foodstuffs

An evaluation of a method based on solid phase extraction (SPE) as a clean- up stage for the determination of pesticide residues in composite vegetable and cabbage samples is presented. Samples are extracted with acetonitrile and the extract is loaded onto an SPE cartridge. The pesticides are eluted with a mixture of acetonitrile/toluene (3:1 v/v) and determined by GC-MS or HPLC with fluorescence detection. Acceptable recoveries were obtained for 31 pesticides. An investigation of the effect of partial, as opposed to exa ct, matrix matching of standards in GC-MS analysis is also presented. While the variation using unmatched standards is visibly greater, the difference is not such as to require exact matrix matching for residue-screening work . The procedure removes the need for chlorinated solvents, reduces the volu mes of other solvents used and allows increased sample throughput compared with liquid-liquid extraction procedures. (C) 1999 Society of Chemical Indu stry.