Abstract: Trace chromium (VI) catalyzes the oxidation of crystallized violet and methyl green by potassium chlorate in dilute H2SO4 solution, which will cause the discoloring of the solution. A dual-wavelength and dual-indicator catalytic kinetic spectrophotometric method to quantify the concentration of chromium (Ⅵ) was proposed by determining the difference of absorbance (δA) of the reaction solution with and without trace chromium (Ⅵ) as catalyst. The results showed that limit of detection of the proposed method was 0.003 mg/L and that the recovery for chromium (Ⅵ) was between 98.3% and 102.0% with a relative standard deviation of less than 2.7%. The linear range was 0.045－0.200 μg/mL. Our results demonstrate that this method is simple, convenient and applicable in practice.

Key words: dual-wavelength spectrophotometry, chromium, food