Author
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KING, JERRY |
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Zhang, Zhouyao |
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Submitted to: Analytical Chemistry
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/1/1998 Publication Date: N/A Citation: N/A Interpretive Summary: Analysis of the pesticide content in various food products is routinely done by many governmental regulatory agencies. For foods containing appreciable amounts of fat, one must separate the fat-containing compounds from the pesticides before analysis methods are applied. This step requires additional time and expense to obtain a food extract devoid of fats. Recently, high pressure carbon dioxide has been applied for the extraction of pesticides from various foods to overcome some of the environmental and laboratory safety concerns in using toxic and flammable liquid solvents for the same purpose. As with the liquid solvent extractions, pressurized carbon dioxide extraction coextracts unwanted fats, which must be removed before the analysis for pesticides is conducted. In this study, conditions were optimized for the removal of the desired pesticides from the food matrix, minus the unwanted fatty material. This was accomplished by using a high pressure nitrogen/carbon dioxide mixture, rather than pure carbon dioxide. The results of applying the gas mixture was an extract relatively free of all fats that would interfere in the subsequent assay for pesticides in the extract. Therefore, this research has generated a safer, more efficient method for analyzing foods for pesticide content, resulting in considerable time savings in the analysis method. This should allow for the more rapid analysis of foods for their pesticide content, thereby protecting both the American and foreign consumer from these objectionable chemical residues in their food. Technical Abstract: When supercritical fluid 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 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. 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 CO2/nitrogen binary fluid mixture demonstrated sufficient solvation power for quantitative recoveries of trace fortified organophosphorous 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 cleanup the extract. |
