Supercritical fluid-based cleanup technique for the separation of organochlorine pesticides from fats

Abstract

A supercritical fluid cleanup technique for the separation of organochlorine pesticides from fats has been developed. The technique uses either an alumina column or a silica column with a supercritical mobile phase of carbon dioxide or methanol/carbon dioxide (2 mol % methanol), respectively. The lipid matrices were chicken fat with incurred residues of heptachlor epoxide, dieldrin, and endrin at low parts per million levels and lard spiked with lindane, heptachlor, hetachlor epoxide, dieldrin, en· drin, and o,p'·DDTat low parts per million levels. Recoveries (93-111 %) and precision (% RSD S 8.5) obtained with the supercritical fluid technique compare favorably with those obtained by conventional column cleanup methodology. In recent years, interest in the use of supercritical fluid extraction (SFE) as an analytical technique has increased considerably (Hawthorne, 1990). An interesting appli­ cation ofthis technology is in the field ofpesticide residue analyses. For instance, McNally and Wheeler (1988a,b) applied SFE to the analysis of sulfonylureas in soil, plant materials, and cell culture media. Engelhardt and Gross (1988) reported the analysis of lindane, aldrin, and p,p/. DDT in a spiked soil sample using SFE combined with supercritica1 fluid chromatography(SFC). Basicsolubility studies of pesticides in supercritical carbon dioxide have been conducted by Schafer and Baumann (1988, 1989). Recently, Lopez·Avila et al. (1989) reported the SFE of 17 organochlorine pesticides and 25 organophosphorus pesticides from sand using carbon dioxide or acetone­ modified carbon dioxide.