AbstractIn conjunction with a study of herbicide degradation in the field, metribuzin (4‐amino‐6‐tert‐butyl‐4,5‐dihydro‐3‐methylthio‐l,2,4‐triazin‐5‐one) was shown to be degraded at‐37±5°C in soil samples awaiting analysis. Products of this degradation process include the known derivatives DADK (6‐tert‐butyl‐2,3,4,5‐tetrahydro‐l,2,4‐triazine‐3,5‐dione) and DK (4‐amino‐6‐tert‐butyl‐2,3,4,5‐tetrahydro‐l,2,4‐triazine‐3,5‐dione) and these products themselves have been shown to be degraded further under the same storage conditions. Loss of the herbicide can be approximated using half order kinetics with respect to metribuzin; however, loss of both previously identified metabolites is most rapid when metabolite concentrations are highest. Assuming half order kinetics, samples of Almasippi very fine sandy loam containing metribuzin (0.5 mg/kg) can be expected to lose 50% of the herbicide in 282 days at ‐ 37°, a period which is short enough to affect residue analysis results significantly should samples be stored for extended lengths of time prior to analysis. Implied in these results is the desirability of immediate analysis following collection of samples; otherwise rates of loss during storage must be determined to allow adjustment of res
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