Amperometric determination of organic isothiocyanates

An amperometric titration method is described for the determination of 1-5 mg of organic isothiocyanates, based on their quantitative reaction with n-butylamine in dimethylfonnamide to form N,N-disubstituted thioureas which are then titrated amperometrically in aqueous ammonia-ammonium nitrate buffer with silver nitrate (dropping mercury electrode at -0.56V). The end-point corresponds to a silver:thiourea ratio of 2:1, with precipitation of silver sulphide. The method is simple, accurate, widely applicable, and gives reproducible results.