Determination of phenolphthalein in pharmaceutical preparations using N-bromosuccinimide

Abstract

Phenolphthalein was determined by direct titration in 0.04M sodium hydroxide solution with N-bromosuccinimide. Micro-elemental analysis and infrared spectroscopy of the reaction product indicated that it was tetrabromophenolphthalein. The method was compared with the US National Formulary method. Amounts of 0.318–11.13 mg of phenolphthalein were determined by this method, the recovery being 100.13 ± 0.72%. The compound was determined in several pharmaceutical formulations. Other laxatives found in combination with it, such as aloin and podophyllin, do not interfere.