Gas-liquid chromatographic determination of nonpolar organochlorine pesticide residues in a crude vegetable oil and its refinery by-products.

A crude soybean oil, several of its refinery by-products (described as soapstock, deodorizer distillate, and clabber stock), and the completely refined oil were analyzed for pesticide residues. Fourteen organo-chlorine pesticides and pesticide metabolites were found in the deodorizer distillate; 5 of these were also found in the clabber stock. Levels in these by-products ranged from 0.3 to 8 ppm. Only endrin and dieldrin were detected in the crude oil at levels of 0.01 and 0.05 ppm, respectively. Forty to 150 times these levels were found in the deodorizer distillate and clabber stock. Pesticide residues were not detected in the refined oil or in the soapstock at limits of detection for dieldrin of about 0.01 and 0.1 ppm, respectively. The method used by the Food and Drug Administration to analyze fats and oils for multiple organohalogen pesticide residues was inadequate for the extraction of pesticide residues from vegetable oil refinery by-products. The method used to analyze the crude vegetable oil and the refinery by-products involved dissolution of the oil samples in ethyl acetate-toluene, filtration if necessary, cleanup by gel permeation chromatography, and then Florisil column chromatography. The oil was isolated from aqueous-oil mixtures by extraction with hexane before analysis. The crude soybean oil was fortified with 12 organohalogen pesticides and Aroclor 1254 at levels of 0.5-3.7 ppm. Recoveries ranged from 83 to 102%.

Quality assurance in the analysis of foods and trace constituents.

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.

Determination of hexachloro-1,3-butadiene in spinach, eggs, fish, and milk by electron capture gas-liquid chromatography.

Hexachloro-1,3-butadiene (HCBD), a waste product formed in the manufacture of perchloroethylene and trichloroethylene, has been found in fish from the lower Mississippi River basin. The AOAC official method for organochlorine pesticide residues in fatty and nonfatty foods has been modified for the determination of HCBD residues in selected food commodities. Acetonitrile extracts of nonfatty foods, or the combined acetonitrile extracts obtained in acetonitrile-petroleum ether partitioning of fat isolated from fatty foods, are diluted with water and extracted with petroleum ether. The petroleum ether extracts are chromatographed on Florisil and HCBD is eluted with petroleum ether. The elute is analyzed by gas-liquid chromatography with an electron capture detector. Average recoveries of HCBD from fortified samples of fatty and nonfatty foods were greater than 90% in the interlaboratory trials of the method.

Gas-liquid chromatographic determination of kepone residues in finfish, shellfish, and crustaceans.

Finfish, shellfish, and crustacean samples are extracted with isopropanol and benzene; the extract is filtered and then concentrated. The extract, dissolved in hexane, is treated with oleum and extracted with aqueous alkali. The aqueous phase is acidified and extracted with petroleum ether-ethyl ether (1 + 1). The Kepone residue is determined by electron capture gas-liquid chromatography (GLC). Recoveries obtained by 8 laboratories from 15 species of finfish fortified at 0.02-0.23 ppm ranged from 37 to 107% with a mean +/- relative standard deviation of 79.4 +/- 14.5%. For oysters fortified at 0.01-0.10 ppm, recoveries range from 63 to 129% with a mean of 78.8 +/- 20.8%. For crustaceans fortified at 0.05-0.26 ppm, recoveries ranged from 52 to 110% with a mean of 78 +/- 16.4%. The approximate limits of quantitation for finfish and for shellfish and crustaceans are 0.02 and 0.05 ppm, respectively, under the GLC conditions used in this study.

Induction of aryl hydrocarbon hydroxylase activity in cell cultures by aroclors, residues from yusho oil samples, and polychlorinated biphenyl residues from fish samples.

Four Aroclor reference materials, cleaned-up extracts of 2 yusho rice oil samples, and cleaned-up extracts of 3 fish samples containing polychlorinated biphenyl (PCB) residues were tested for their ability to induce aryl hydrocarbon hydroxylase (AHH) activity in a rat hepatoma cell line. Before the AHH bioassay, the samples were fractionated by a Florisil column chromatographic method. All samples contained about 1000 micrograms PCBs before Florisil column chromatography. The first Florisil eluate contains about 95% of the PCBs in a typical Aroclor, and the second contains the more polar or adsorbent PCB congeners. In this study, the first eluate for all samples produced no quantifiable AHH activity. The second Florisil eluates of both Aroclors 1242 and 1248 induced AHH activity, whereas these eluates of both Aroclors 1254 and 1260 did not. This difference may be due to the presence in Aroclors 1242 and 1248 of 3,3',4,4'-tetrachlorobiphenyl, which has not been detected in Aroclors 1254 and 1260. The second Florisil eluates of the fish samples induced somewhat less AHH activity than did Aroclor 1242 or 1248. The second Florisil eluates of the PCB residues from yusho rice oil samples induced significantly greater AHH activity than these eluates of either Aroclor 1242 or 1248, perhaps because yusho rice oil contains a greater amount of polychlorinated dibenzofurans than PCB commercial mixtures on a PCB equivalent basis.