研究了在邻苯二甲酸氢钾-盐酸缓冲溶液(pH 2)中,硒(Ⅳ)对硫化钠还原二甲酚橙的褪色反应具有催化作用.结果表明:催化反应是准零级反应,反应的表观速率常数为7.67×10-5mol·L-1·s-1,表观活化能为50.09 kJ·mol-1.催化反应吸光度A0与非催化反应吸光度A的差值ΔA与硒(Ⅳ)的质量浓度在0.12 mg·L-1以内呈线性关系,方法的检出限为2.66×10-5g·L-1.用于水样中痕量硒(Ⅳ)的测定,结果满意.

In a phthalate buffer medium of pH 2,the catalytic action of Se(Ⅳ) on the reductive color-fading of xylenol orange by sodium sulfide was studied. It was found that the catalytic reaction was a zero order reaction,the apparent constant of reaction rate was found to be 7.67×10-5mol·L-1·s-1,and the apparent activation energy was 50.09 kJ·mol-1. Linear relationship between values of ΔA (difference of absorbances between the catalytic and non-catalytic reactions) and concentration of Se(Ⅳ) was obtained within 0.12 mg·L-1 of Se(Ⅳ),with a detection limit of 2.66×10-5g·L-1. The proposed method has been applied to the determination of traces amounts of Se(Ⅳ) in water samples.