Thermometric assay of some sulphonamides of pharmaceutical importance

Abstract

The thermometric determination of several sulphonamides used in pharmaceutical preparations is described. The sulphonamide is dissolved in the minimum amount of dilute sodium hydroxide solution and the pH adjusted to 8·9 with thymolphthalein as indicator. The solution is then made up to 10 cm³ with an appropriate buffer solution (pH 8·0 or 9·18). In these controlled alkaline conditions, the sulphonamide is titrated directly with silver nitrate solution, the equivalence point being determined thermometrically. The effects of several matrix ingredients in common use in pharmaceutical preparations have been determined. The time of the titration is approximately 1 minute and the accuracy is within ±2 per cent.