Search

Thirty-five samples of vitamin E supplement softgels, obtained from store shelves, were analyzed for 17 dioxin and furan congeners. Of these samples, 14 were identified as natural vitamin E, containing D- α -tocopherol, as well as lesser amounts of β -, α -, and δ -tocopherols, and the remaining 21 were labeled as synthetic vitamin E, containing a mixture of D- and L- α -tocopherol. The supplements were collected during the years of 2002 and 2004. The seven natural vitamin E supplements collected in 2002 were found to contain significant quantities of dioxins and furans, with an average total toxic equivalence (TEQ) of 0.79 pg/g, compared to 0.10 g/g for the 2004 natural vitamin E supplements. The 21 synthetic vitamin E supplements collected during the same time period showed little or no contamination, with an average TEQ of 0.057 pg/g. Eight samples of deodorizer distillate, from which natural vitamin E is derived, were also collected and analyzed. The distillates exhibit an overall congener pattern similar to that found in the natural vitamin E, but at a much higher average TEQ of 3.4 pg/g. This suggests the possibility of carryover of contamination to the vitamin E samples from the deodorizer distillate during the extraction process. The natural vitamin E supplements collected in 2004 have much lower levels of contamination, suggesting that improved extraction processes may be in use, effectively reducing contamination.

Oxidation of lidocaine and its principal metabolites, monoethylglycine xylidide and glycine xylidide, at glassy carbon electrodes was employed to permit electrochemical detection of these compounds following separation by high-performance liquid chromatography. The absolute detection limits found for these compounds were 2 ng, 5 ng, and 4 ng injected, respectively. The resulting assay was suitable for the routine quantitation of lidocaine and these metabolites in blood serum over the entire therapeutic range, 1-6 micrograms/ml. Total analysis time is 10-15 min.

Cobalt phthalocyanine-containing carbon paste electrodes are used as electrocatalytic amperometric sensors for 6-mercaptopurine, 6-thioguanine, and several related thiopurines in blood plasma after separation by liquid chromatography. Required sample preparation is minimal, and total quantitation time is 8 min or less. Detection limits are 1.5–8 pmol, approximately an order of magnitude better than that obtained with ultraviolet or fluorescence detection.