Selective extraction of pesticides from lipid-containing matrixes using supercritical binary gas mixtures

When supercritical carbon dioxide is used for extraction of trace compounds from lipid-rich samples, the resulting extract can contain a substantial amount of lipid coextractive which interferes in the subsequent chromatographic analysis. In this case, a cleanup step, which is time-consuming, is required in order to remove or reduce the lipid content in the extract. In this study, we report on a new approach for the extraction of trace compounds which significantly reduces the quantity of lipid coextractives, thereby eliminating the need for a sample cleanup step. An autoclave high-pressure reactor equipped with a mechanical stirring device was used for mixing gases, such as carbon dioxide and nitrogen, to generate the desired fluid mixtures. The composition of the mixtures could be adjusted by two mass flow controllers prior to the autoclave mixing device. The generated carbon dioxide/nitrogen binary mixtures were then employed to facilitate supercritical fluid extraction (SFE) at high pressures and elevated temperatures. The pressurized CO(2)/nitrogen binary fluid mixture demonstrated sufficient solvation power for quantitative recoveries of trace fortified organophosphorus and incurred organochlorine pesticides from poultry fat while significantly reducing lipid solubility in the fluid. This allowed the development of a method that produced an extract with minimal lipid content that could be used directly for gas chromatographic analysis, thereby eliminating the need to clean-up the extract.