INDIRECT SPECTROPHOTOMETRIC DETERMINATION OF HYDROGEN-PEROXIDE

Abstract

A method for the indirect spectrophotometric determination of H2O2 is based on its oxidation with chlorine in basic medium and measurement of the unreacted Cl2 by the colour reaction with o-tolidine at 438 nm. The effective molar absorptivity for H2O2 with o-tolidine is 5.37 x 10(4) mol-1 cm-1 at pH 1.7. The lower limit of determination is 1.85 x 10(-7) mol/l or 6.29 ppb. Br-, I-, NO2-, Pb2+ and Sn2+ interfere even in small amounts, but are not present in commercial H2O2.