Kinetic spectrophotometric determination of some sulfur containing compounds in pharmaceutical preparations and human serum.

Abstract A kinetic spectrophotometric method was developed for the determination of carbocisteine, ethionamide, thioctic acid and penicillamine based on the catalytic effect on the reaction between sodium azide and iodine in aqueous solution. Ten to 100 μg ml −1 of carbocisteine and ethionamide, 0.1–1 μg ml −1 of thioctic acid and 0.01–0.1 μg ml −1 of penicillamine could be determined, respectively, by measuring the decrease in the absorbance of iodine at 348 nm by a fixed time method. The decrease in the absorbance in the first 5 min from the initiation of the reaction is related to the concentration of the drugs. The detection limits were 0.47, 0.71, 0.018 and 9.38×10 −4 μg ml −1 for the four drugs, respectively. The proposed procedure was successfully applied in the determination of these drugs in pharmaceutical preparations and human serum.