Gels chromatographic analysis of methiocarb and its metabolites in soil and rice

A new method to determine the amount of methiocarb and its two metabolites, the sulfoxide and sulfone in soil and rice plant is described. The method consists of extraction of samples with acetone, filtration, separation of m ethiocarb and its metabolites through a Florisil column, and gas chromatogr aphic determination. Since the degradation of methiocarb to 3,5-dimethyl-4- methylthiophenol (DMMP) is commonly observed during GC analysis, methiocarb was converted to DMMP via chemical hydrolysis after column chromatography. Reasonable recoveries for routine analysis were obtained and the limit of quantitation (LOQ) with GC/FPD were 0.5, 2 and 2 ng for DMMP: sulfoxide and sulfone, with a signal to noise ratio of 4. In all rife samples, no detect able residues were found, however DMMP and methiocarb sulfoxide were found in some straw samples. In field soil samples, no sulfone was detected in al l samples and methiocarb showed typical degradation curves with a half life of 8 days after treatment. A five-fold longer half life was observed in in door studies.