Oxidants for the colorimetric determination of pindolol

A simple, sensitive and accurate colorimetric method is described for the quantitative determination of pindolol either in the pure form or in its tablets. The method is based on the oxidation of the indole moiety in pindolol with potassium persulphate or hydrogen peroxide-in acid medium-to give a highly coloured product that exhibits maximum absorption at 535 nm and 570 nm, respectively. Beer's law is obeyed over concentrations ranging from 0.07-0.35 mg/10 ml for potassium persulphate and 0.1-0.5 mg/10 ml for hydrogen peroxide with mean recoveries of 99.6+/-0.6 and 99.8+/-0.9%, respectively. The method is applied for the assay of pindolol tablets without any interference due to tablet fillers.