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

H(2)O(2) in marine waters may be determined by measuring the absorbance of crystal violet (CV(+)), formed by the oxidation of leuco crystal violet (LCV) by H(2)O(2) 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 muM and +/- 1% (at a concentration of 0.03 muM), 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 H(2)O(2).