On the pretreatment for photometric determination of carbaryl in unpolished rice

The determination of insectiside, 1-naphthyl-N-methylcarbamate (NAC) in unpolished rice has been made by the photometric method with pretreatment. This work involved the extraction of NAC with CH2Cl2- (CH3) 2CO-H2O (1: 1: 1), the clean-up procedures consisted of distirbution between n-hexane and acetonitrile, and of alumina column and active carbon column chromatography. The eluates were concetrated and NAC was hydrolyzed to corresponding phenol, which was then coupled with 4-nitrobenzenediazonium ion to produce colored compound. It was dissolved in methanol and determined by colorimetry. The recovery of NAC added to unpolished rice was 90%. This method can be applied to the test of NAC residues in unpolished rice produced.