An indirect enzyme-linked immunosorbent assay (EIA) for metolachlor (2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamid e) detection in river water and soil was developed using serum obtained from rabbits immunized against the acid of metalaxyl ((N-(2,6-dimethylphenyl)-N-(methoxy-acetyl)-DL-alanine methyl ester) conjugated to bovine serum albumin. The assay had a linear working range from 1 to 50 ng/ml with a mean I50 value of 13.6 ng/ml and a lower detection limit of 2.0 ng/ml. Both the mean interwell and interassay coefficients of variation were less than 4% over the range of the standard curves for samples which had been prepared in phosphate buffered saline (PBS), river water, or soil extract. Assay cross-reactivity to the following four structurally related chloro-acetanilide pesticides were: propachlor (0%), metazachlor (0%), alachlor (23%), and metalaxyl (5,000%). Mean recoveries of metolachlor in spiked (2.0 to 32.0 ng/ml range) PBS, river water, and soil extract were 102%, 103%, and 110%, respectively. Soil samples were taken over a 56-d period from field plots treated with metolachlor and analyzed by GC and EIA. The correlation coefficient for comparison of the two methods was 0.96 with the slope of the linear regression line being 0.78. Furthermore, no statistical difference (P less than 0.05) was found between the dissipation curves of metolachlor derived from GC data versus EIA data.
A method for determining chloroform, 1,1,1-trichloroethane, carbon tetrachloride, and trichloroethene in breath samples was developed. It consisted of collecting samples in 40-ml. glass-silanized tubes that were 16-in. long and had a 0.64-in. diameter. The ends tapered, resulting in a tube with a 1/4-in. diameter that was 1 3/4-in. long; each end had a shutoff valve attached. One end had a strip of rubber tube attached to the shutoff valve for collecting the breath sample, and the other end contained a 1/4-in. Swagelok nut with a rubber septum for withdrawing the sample. Samples were withdrawn using a pressure-lock, gastight syringe, and they were injected onto a gas chromatograph fitted with an electron-capture detector. The analytes were stable for at least 22 days in these tubes. The method detection limit was determined to be 0.03, 0.08, 0.04, and 0.04 pg/ml. for chloroform, 1,1,1-trichloroethane, carbon tetrachloride, and trichloroethene, respectively. Precision, based on 13 injections, was determined to be 13% for 0.09 pg chloroform, 13% for 0.21 pg 1,1,1-trichloroethane, 8% for 0.16 pg carbon tetrachloride, and 14% for 0.1 pg trichloroethene. In all, the proposed method is a sensitive and reliable one for determining volatile organic compounds in breath and a method that can also be applied to air sampling.
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