Determining organohalides in animal fats using gel permeation chromatographic cleanup: repeatability study

Evaluation of a previously published gel permeation chromatographic (GPC) procedure was undertaken to determine whether it can be used for additional organochlorine pesticides. After repeatability studies of many pesticides, the following compounds were approved for inclusion in the U.S. Department of Agriculture Domestic Residue Monitoring Program: coumaphos-S, stirophos, chlorpyrifos, ronnel, carbophenothion, chlorfenvinphos, phosalone, kepone, captan, linuron, and endosulfan I and II. Recoveries ranged from 54% for captan to 123% for ronnel. Ranges of CVs varied from 0-9.5% for carbophenothion to 7.1-47.7% for kepone. Although the minimum acceptable recovery of 50% was attained for all 12 pesticides, the anticipated CV of 20% was waived to include chlorpyrifos, endosulfan I and II, and kepone. For a multiresidue procedure involving approximately 40 compounds, these results were within the acceptable criteria.