Potentiometric titration method: Indian Pharmacopoeia (1996), recommended that a solution of drug in buffer (about 50 mg, dissolved in 10 ml of alkaline borate buffer pH 9.0 and 0.2 ml of acetic anhydride and stirred for 3 minutes. Added 10 ml of 1M sodium hydroxide and allowed to stand for 15 minutes. Added 10 ml of 1M nitric acid and 20 ml of acetate buffer pH 4.6) titrated with 0.02 M mercuric nitrate, determining the end‐point
potentiometrically with a platinum or mercury indicator electrode and a mercury‐mercurous sulphate reference electrode and disregarding any preliminary inflection in the titration curve.