| As the shock wave from the passing of the Food Quality Protection Act of 1996 subsides, the effects upon analytical methods have begun to emerge. In particular the method sensitivities for many compounds being registered on food crops are being lowered to better estimate risk. As a result, current methodologies are either inadequate or require substantial modification to achieve the mandated lower method sensitivity.; In terms of minor use crops, three new methods were developed for pesticide determination in studies that focus on magnitude of residues. The first method was developed for the analysis of the herbicide MCPB (2-methyl-4-chlorophenoxybutyric acid) and its major metabolite, MCPA (2-methyl-4-chlorophenoxyacetic acid) in edible peas (peas, peas with pods, and dry peas) down to 0.01 part per million (ppm). The second method was developed for the analysis of the fungicide cymoxanil (2-cyano-N-[(ethylamino)carbonyl]-2-(methoxyimino)acetamide) in dried hop cones down to 0.05 ppm. The third, another dried hop method, was developed to analyze for the fungicide dimethomorph ((E,Z)-4-[3-(4-chlorophenyl)-3-(3,4-dimethoxyphenyl)acryloyl]morpholine) with a method sensitivity of 0.1 ppm.; The analysis of pesticides on dried hops posed interesting challenges to many of the current cleanup practices used on other crops. Dried hops have large concentrations of lipophilic constituents (waxes, resins, oils, and pigments) that tend to be co-extracted along with the pesticides during the initial extraction and liquid partition steps. Therefore it was necessary to utilize gel permeation chromatography (GPC) to separate the pesticides from the matrix components. Although the GPC removed the bulk of the background matrix a noticeable yellow coloration remained and was subsequently removed by packed columns and/or solid phase extraction. As a result of the extensive cleanup process, the samples were suitable for analysis via gas chromatography.; In addition to methods developed for crops, attention has been focused on beverages that utilize agricultural commodities. In the production of beer, hops are a major constituent that adds bitterness, flavor, and aroma. Currently several pesticides: chlorfenapyr, quinoxyfen, tebuconazole, fenarimol, pyridaben, and dimethomorph are being considered for registration on hops in the United States. Studies conducted by the Interregional Research Project No. 4 (United States Department of Agriculture) have shown residues as high as 10 ppm and greater. Given the relatively high residues, the potential for carry over into the final product would suggest the need for investigation into the fate of these pesticides during the brewing process.; Methodologies were developed to address the various matrixes (wort, beer, trub, and spent hops) in order to quantify pesticide residues, if any. In order to evaluate the fate of the aforementioned compounds, field treated hop samples were used during the brewing process. Subsequent analyses of the various brewing fractions suggested that more than 89% of the compounds of interest remained in the spent hops, while only a small fraction, less than 0.008 ppm, were detected in the wort.; In addition to the brew trial with treated hops, a fermentation study was conducted to determine the fate of residues, which have carried over into the wort. Results show a dramatic drop in the non-polar pesticides, while the more polar pesticides show a much slower reduction in residue levels. Analysis of the trub (sediment) following the completion of fermentation shows that the majority of the non-polar and the remainder of the polar compounds were sequestered there. |
