Colorimetric determination of propoxur and its residues in vegetables

A method has been developed for the determination of propoxur (o-isopropoxyphenyl N-methylcarbamate) based on the hydrolysis of propoxur with methanolic potassium hydroxide to its phenol and coupling with diazotized 4,4-diaminodiphenyl sulfone. The orange complex formed has an absorption maximum at 500 nm and obeys Beer's law in the range 0.25-5.0 micrograms/mL. The method can be applied to levels as low as 0.5 ppm propoxur from vegetables.