在pH 1.7的柠檬酸盐缓冲介质中,在沸水浴中加热10 min痕量钒(Ⅴ)使5-Cl-PADAT被过氧化氢氧化而褪色的反应受到抑止.在此反应体系中加入钒(Ⅴ)及不加钒(Ⅴ)在其吸收峰460 nm处所测得的吸光度A及A0的差值ΔA与钒(Ⅴ)浓度在0-91.8 ng/25 mL范围内呈线性关系.检出限为7.19×10-9g·L-1.常见的共存离子不干扰钒(Ⅴ)的光度测定.研究了反应的动力学参数,给出在不同钒(Ⅴ)及过氧化氢浓度的下的反应速率常数.用作图积分法处理试验结果,证明无论是5-Cl-PADAT与过氧化氢及钒(Ⅴ)的反应或5-Cl-PADAT与过氧化氢的反应均属零级反应.两反应的表观活化能依次为82.1 及61.6 kJ·mol-1.反应最佳温度条件为100 ℃,反应已应用于血样及茶叶中痕量钒的测定；RSD在1.8%-2.6%之间,回收率在98.1%-105.0%之间.

In a citrate buffer of pH 1.7 and heated for 10 min in boiling water bath,the oxidative color-fading of 5-Cl-PADAT by H2O2 was inhibited by traces of vanadium(Ⅴ).Difference of absorbance (ΔA) of solutions in the presence of V(Ⅴ) (A) and in the absence of V(Ⅴ) (A0) measured at λmax 460 nm kept a linear relationship with the concentration of vanadium(Ⅴ) in the range of 0-91.8 ng per 25 mL of solution.Its detection limit was found to be 7.19×10-9g·L-1.Most of the common co-existing ions did not interfere the determination.Kinetic parameters of the oxidation reaction were also studied.It was concluded on the results of graphical integration that both the reaction with V(Ⅴ) and H2O2 or with H2O2 only,were of zero order.The apparent activity energy were found to be 61.6 kJ·mol-1 and 82.1 kJ·mol-1 for reactions of R+H2O2 and R+H2O2+V(Ⅴ) respectively.The optimum temperature of heating for the reaction was 100 ℃.RSD′s in the range from 1.8% to 2.6% and recoveries in the range from 98.1% to 105.0%,were found in the analysis of blood and tea samples.