Spectrophotometric and kinetic determination of some sulphur containing drugs in bulk and drug formulations

Two simple and sensitive spectrophotometric methods were developed for the determination of carbocisteine, penicillamine, ethionamide and thioctic acid in bulk and in their pharmaceutical preparations using alkaline potassium permanganate as an oxidizing agent. The first one involves determination of ethionamide and thioctic acid by spectrophotometric investigation of the oxidation reaction of the two drugs. The second method involves determination of carbocisteine and penicillamine by kinetic studies of the oxidation reaction of these two drugs at room temperature for a fixed time of 20 minutes. The absorbance of the colored manganate ions was measured at 610 nm in both methods. 1-10 mug/mL of ethionamide and thioctic acid could be determined by the spectrophotometric method with detection limits of 0.11 and 0.089 mug/mL for the two drugs respectively. 2-10 mug/mL of carbocisteine and penicillamine could be determined by the kinetic method with detection limits of 0.14 and 0.21 mug/mL respectively. The two methods were successfully applied for the determination of these drugs in their dosage forms.