SIMULTANEOUS DETERMINATION OF N-METHYLCARBAMATE PESTICIDES IN AGRICULTURAL PRODUCTS BY LIQUID-CHROMATOGRAPHY

Simultaneous determination of N-methylcarbamate pesticides in agricultural products by high performance liquid chromatography with post-column fluorescence derivatization was investigated. The food sample homogenate was extracted with acetone. The crude extract was partitioned between 5% sodium chloride solution and dichloromethane, and the dichloromethane layer was concentrated to dryness. The residue was dissolved in methanol, dilute hydrochloric acid was added and the solution was analyzed by liquid chromatography with post-column fluorescence derivatization. The post-column reaction system uses a two-step reaction: N-methylcarbamate hydrolysis by NaOH solution cleaves off methylamine, which reacts with o-phthalaldehyde and 2-mercaptoethanol. The resulting fluorescent derivative was detected at 445 nm (excitation at 339 nm). Recovery at the 0.1 ppm levels was around 90% with a coefficient of variation of about 5%. The detection limit was 0.005 ppm in samples. The method is recommended for determination of residues of N-methylcarbamate and its metabolites in foods.