Catalytic Photometric Determination of Trace Amount of Selenium(Ⅳ) in Human Hair

In 0.025 mol·L-1 H2SO4 medium and heated in a water bath at 90 ℃ for 12 min, the oxidative color-fading reaction of alkali blue by potassium bromate was remarkably catalyzed by the presence of trace amount of Se(Ⅳ). Based on these facts, a catalytic photometric method for determination of trace amount of Se(Ⅳ) was proposed. It was proved that in the catalytic process, it was a pseudo-zero order reaction for alkali blue and a pseudo-first order reaction for Se(Ⅳ). The apparent activation energy of the catalytic reaction and non-catalytic reaction were found to be 46.13 kJ·mol-1 and 65.16 kJ·mol-1 respectively. Linear relationship between the values of decrease in absorbance (ΔA) and mass concentration of Se(Ⅳ) was obtained in the range within 40 μg·L-1. Detection limit (3s/k) found was 2.75×10-3μg·L-1. In analyzing sample of human hair by this method, result of Se(Ⅳ) found was in consistency with the result found by GF-AAS method.