A simplified rapid method is presented to determine organochlorine pesticides and polychlorinated biphenyls in fish. Samples are mixed with sodium sulfate and blended with petroleum ether. A portion of the blend is placed on a miniaturized Florisil column and compounds are eluted with mixtures containing 6 and 15% ethyl ether in petroleum ether. Gas-liquid chromatography with electron capture detection comparable to the official methods (29.018) is used for determination of residues. Each of 7 collaborators reported results in duplicate for 10 samples containing one or more of the following compounds: p,p’-DDD,p,p’-DDE, p,p’-DDT, dieldrin, heptachlor epoxide, Aroclor 1254, and Aroclor 1260. Recoveries ranged from 79.3 to 100.7%. The coefficients of variation between laboratories ranged from 6.3 to 20.6%. This method allows up to 80% reduction in reagents and up to 50% reduction in analytical time, and requires less laboratory space than current official methods. The method has been adopted official first action.

In 1993-94, the U.S. Food and Drug Administration (FDA) conducted a statistically based study of pesticide residues in domestic and imported fresh apples and processed rice. For apples, 769 domestic and 1062 imported samples were collected and analyzed; 85% of the domestic and 86% of the imported samples had detectable residues. Benomyl, a widely used fungicide, was found with greatest frequency in domestic apples, while diphenylamine was found most often in imported apples. One domestic and 4 imported samples contained violative residues of pesticides for which there are no U.S. tolerances on apples. The statistically weighted (by domestic packer throughput or import shipment size) violation rates for domestic and imported apples were 0.30% (0.13 unweighted) and 0.41% (0.38 unweighted), respectively. For rice, 598 domestic and 612 imported samples were collected and analyzed; 56% of the domestic and 12% of the imported samples had detectable residues. Malathion had the greatest frequency of occurrence in both groups of rice. Eight domestic and 9 imported samples were violative, all as a result of use of pesticides for which there are no U.S. tolerances on rice. The statistically weighted violation rates for domestic and imported rice were 0.43% (1.3 unweighted) and 1.1% (1.5 unweighted), respectively. Results of the statistically based study show that, as in FDA’s regulatory monitoring, the levels of most pesticide residues found in these 2 commodities are generally well below U.S. tolerances, and few violative residues are found.

In 1992–1993, the U.S. Food and Drug Administration (FDA) conducted a statistically based study of pesticide residues in domestic and imported pears and tomatoes. For pears, 710 domestic and 949 imported samples were collected and analyzed; 79% of the domestic and 72% of the imported samples had detectable residues. Thiabendazole, a fungicide with postharvest uses, was found with greatest frequency in both groups of pears. Four domestic and 12 imported samples contained violative residues, mainly of pesticides for which there are no U.S. tolerances on pears. The statistically weighted (by shipment size) violation rates for domestic and imported pears were 1.0 and 0.9%, respectively. For tomatoes, 1219 domestic and 144 imported samples were collected and analyzed; 84% of the domestic and 91% of the imported samples had detectable residues. Methamidophos, an insecticide, had the greatest frequency of occurrence in both groups of tomatoes. Thirtythree domestic and 5 imported samples were violative, nearly all the result of acephate use, for which there is no U.S. tolerance on tomatoes. The statistically weighted violation rates for domestic and imported tomatoes were 1.9 and 7.0%, respectively. The statistically weighted violation rates calculated for domestic and imported pears and domestic tomatoes in this study were lower than those observed under FDA’s regulatory monitoring in recent years. The violation rate for imported tomatoes was somewhat higher under statistical monitoring than under regulatory monitoring. The results of the statistically based study show that, as in regulatory monitoring, the levels of pesticide residues found are generally well below U.S. tolerances.

A procedure is described for the isolation and cleanup of hexachlorobenzene (HCB) and mirex in fats and oils for gas-liquid chromatographic (GLC) analysis. The fat or oil is distributed on unactivated Florisil, and the HCB and mirex are eluted with acetonitrile. The pesticides are then partitioned into petroleum ether. Elution through activated Florisil with methylene chloride-hexane (20+80) is used for the final cleanup. HCB and mirex are then measured by GLC, using the appropriate electron capture conditions with a 15% OV-210 column for HCB and a 3% OV-101 column for mirex. The method demonstrates recoveries greater than 90% for HCB and mirex and allows screening at or below the 0.1 ppm level in fats with a 3 mg fat injection.

A previously published method applicable to the recovery of hexachlorobenzene (HCB) and Mirex (dodecachlorooctahydro-1,3,4-metheno-2H-cyclobuta (cd) pentalene) from fats and oils has been collaboratively studied by 8 laboratories. The method involves distribution of the fat or oil on unactivated Florisil and elution of the HCB and Mirex with acetonitrile. The 2 compounds are then partitioned into petroleum ether and eluted through activated Florisil with methylene chloride-hexane. Electron capture gas-liquid chromatography is utilized as the determinative step. In the collaborative study, samples of sablefish and butterfat were fortified at 2 different levels; each level was determined in duplicate. Average HCB recoveries of 98±7% and 95±13% at respective levels of 0.06 and 0.5 ppm were obtained from the fish sample. Mirex recoveries in the fish sample at the same levels were 85±l4% and 96±10%. The butterfat sample was fortified at a low level of 0.13 ppm for both compounds and at high levels of 0.62 and 0.66 ppm for HCB and Mirex, respectively. The low level HCB recovery was 104±6% and the high level was 99±10%. In the same order, Mirex was recovered at 104±7% and 103±6%. The method has been adopted as official first action for the determination of HCB and Mirex in fish and fatty dairy products.