Catalytic determination of ultratrace chromium based on gallocyanine‐hydrogen peroxide indicator reaction

Abstract

A highly sensitive catalytic procedure for the determination of ultratrace chromium(VI) was developed based on its catalytic effect on the oxidation of gallocyanine by hydrogen peroxide in hexamine‐hydrochloric acid buffer solution. The reaction was followed spectrophotometrically by measuring the rate of change in the absorbance at 620 nm. The apparent active energy of the catalytic reaction is 6.84 kJ . mol‐1. The calibration graph is linear for 0–150 ng.ml‐1, and the detection limit is 0.8 ng.ml‐1. Most foreign ions have no interfering effect on the determination of chromium(VI) except for Al3+, Cu2+, Fe3+and Fe2+. The interference of Al3+ is eliminated by masking with F‐, and those of Cu2+, Fe3+ and Fe2+ are eliminated by adding appropriate amount of EDTA. The present procedure had been used for the determination of trace chromium(VI) in lake water, mine water and electroplating wastewater, and the results were satisfactory.