Kinetic spectrophotometric determination of oxalic acid based on the catalytic oxidation of Bromophenol Blue by dichromate

A sensitive catalytic method is developed for the spectrophotometric determ ination of oxalic acid. It is based on the catalytic action of oxalic acid on a new indicator reaction - the oxidation of Bromophenol Blue by dichroma te in dilute sulfuric acid medium. The reaction rate is monitored spectroph otometrically by measuring the: absorbance at 600 nm after quenching the re action with sodium hydroxide. A calibration graph from 0.1 to 8.0 mug mL(-1 ) of oxalic acid and a detection limit of 0.04 mug mL(-1) was obtained. The applicability of this method was demonstrated by the determination of oxal ic acid in water extracts from vegetables such as spinach, mushrooms and fr esh kidney beans.