2-Iodoxybenzoate as a titrant for the determination of some pharmaceutically-important thiol compounds

A simple and reliable method was developed for the determination of five pharmaceutical compounds containing thiol group; namely: N-acetylcysteine, D-penicillamine, 6-mercaptopurine, captopril and thioguanine. The method is based on the use of 2-iodoxybenzoate as a titrant in acid medium. The detection of the end point is accomplished potentiometrically, using platinum/calomel electrode combination. For all the studied compounds, the stoichiometry of the reaction was found to be 2:3 suggesting that, the thiol group is oxidised to the corresponding sulphonic acid. This finding was confirmed through TLC study of the reaction products. The proposed method was successfully applied to the determination of the studied compounds in dosage forms and the results were in good agreement with those given using the official methods.