Spectrophotometric determination of the fungicide captan.

A spectrophotometric method for the determination of the fungicide captan has been developed based on its reaction with thiosemicarbazide. The absorbance was measured at 315 nm. The effects of the proportion of water, thiosemicarbazide concentration, pH and temperature on this reaction was studied to select the best chemical conditions. The calibration graph was obtained between 1.2 and 30 ppm and the detection limit is 0.5 ppm. The RSD (n = 10) was 1.34%. Possible interference of various pesticides was examined. The method was applied to the determination of captan in agrochemical formulations. Results agree well with the labelled values and also with results that were obtained by a polarographic method.