Spectrophotometric determination of H(2)O(2) in marine waters with leuco crystal violet

H₂O₂ in marine waters may be determined by measuring the absorbance of crystal violet (CV⁺), formed by the oxidation of leuco crystal violet (LCV) by H₂O₂ in the presence of the enzyme horseradish peroxidase, at 592 nm at pH 4. The detection limit and the precision of the method are about 0.02 μM and ± 1% (at a concentration of 0.03 μM), respectively. The results obtained by this method and by a widely used fluorimetric method agreed with each other well. After color development, samples together with the sub-samples for constructing the calibration curve may be stored for up to 5 days before their absorbances are measured without significantly changing the estimated concentration of H₂O₂.