An examination of the results of over 50 interlaboratory collaborative studies conducted by the AOAC on various commodities for numerous analytes shows a relationship between the mean coefficient of variation (CV), expressed as powers of 2, with the mean concentration measured, expressed as powers of 10, independent of the determinative method. Some typical CV values are: drug formulations at a 1% concentration, 2%; sulfonamides in feeds at a 0.01% concentration, 4%; pesticide residues and toxic elements, 10 6 (1 ppm), 16%; and aflatoxins 10 8 (10 ppb), 32%. Analytical work at trace levels must be constantly monitored through analysis of reference materials and surrogate samples, and by independent replication.
An elution solvent system is presented which can replace the currently used mixtures of ethyl ether-petroleum ether in the Florisil column chromatographic cleanup for pesticide residue analyses. Three eluants consisting of different mixtures of methylene chloride, hexane, and acetonitrile give greatly improved cleanup for extracts of fats and oils and recover pesticide chemicals of a greater range of polarity than do the ethyl ether-petroleum ether eluants. Fifty chemicals are known to be essentially completely recovered. Data are presented on fractional elution of representative compounds and on efficiency of removal of fatty substances. The proposed system has performed satisfactorily as a replacement for the ethyl ether-petroleum ether eluants in the analyses of a variety of representative foods for organochlorine pesticides.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.