Spectrophotometric determination of carbamate pesticides with diazotized trimethylaniline in a micellar medium of sodium dodecyl sulfate.

The spectrophotometric determination of the carbamate pesticides carbaryl, bendiocarb, carbofuran, methiocarb, promecarb and propoxur is proposed. The pesticides are hydrolyzed in alkaline medium to 1-naphthol or phenolates, which are coupled with diazotized trimethylaniline (TMA) in a sodium dodecyl sulfate micellar medium to form the azo dyes. The micellar medium increased the solubility of TMA and enhanced the sensitivity. The performance of TMA was compared with that of sulfanilic acid, which is the conventional reagent used in these determinations. Although the absorbance of the azo dyes of sulfanilic acid was also enhanced in the micellar solution, the sensitivity was still greater with TMA. Further, at the pH required for the coupling reaction (9.5), the absorbance of the blank was negligible with TMA but large with sulfanilic acid. Using TMA, the limits of detection were in the range 0.2-2 micrograms cm-3. The procedure was applied to the determination of carbaryl in spiked tap, river and pond water samples and to the evaluation of various carbamates in commercial pesticide formulations.