Metabolism studies recovery from extraction

Metabolic Studies. To measure EPTC and butylate degradation in soil, aliquots of air-dried Brookston soil were treated with 4 mg kg 1 of EPTC or butylate and incubated at 25°C in the dark. At various intervals, samples were removed from the incubator and EPTC or butylate remaining in the soil was extracted with 10 3 toluene water. The toluene layer was analyzed for EPTC or butylate by GC. The minimum detectable level of EPTC or butylate was 0.05 mg kg"1 soil and the average recovery exceeded 90%. 

These recoveries do not correspond to the 25% recovery of chlorobenzilate found by Bourke and coworkers (6). However, for all treatments except the middle and low chlorobenzilate doses, residues were still detectable at the end of the study period. In most cases the level of residues from the dicofol oral doses began to increase again on days 11 and 12. This was possibly due to mobilization of dicofol stored in fat. We have no explanation for the low recovery data. As mentioned above, it is believed that the sulfuric acid used in the oxidation step was sufficient to cleave any conjugates present. The metabolism literature suggested that the parent compounds would be fully metabolized under our experimental conditions. We analyzed for intact residues in the first few samples and, finding none, we did not continue this practice. Our recoveries were based on spiked samples. Bowman and coworkers (25) have shown that this is risky in the case of crop extractions. Perhaps some mechanisms other than conjugation caused the biologically produced residues to be more difficult to extract than were the fortified samples. 

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