在pH 4.7的乙酸盐缓冲介质中,痕量的铁(Ⅲ)对依文思蓝被过氧化氢氧化的褪色反应具有催化作用,导致依文思蓝褪色的加强.在最佳反应条件下,在622.0 nm波长处所测得反应体系的吸光度的下降程度与铁(Ⅲ)的质量浓度在0.1~20.0 μg·L-1之间呈线性关系.测得此反应的检出限(3s/b)为1.3×10-7g·L-1.应用此方法测定了奶粉、井水及管网水中痕量铁,所测得结果与原子吸收光谱法所测结果一致,测定值的相对标准偏差(n=6)均小于2.5%,回收试验所测得的回收率在99%~102%之间.测得此催化反应体系的表观活化能为34.56 kJ·mol-1,反应速率常数为2.75×10-2s-1.

In an acetate buffer medium of pH 4.7,the oxidation of Evans blue by H2O2 was catalyzed by trace amount of Fe(Ⅲ),leading to enhancement of decoloration of evans blue.Under the optimum condition,linear relationship between the magnitude of decrease in absorbance (ΔA) measured at 622.0 nm and the concentration of Fe(Ⅲ) was found in the range of 0.1 to 20.0 μg·L-1.Detection limit (3s/b) of the method found was 1.3×10-7g·L-1.Samples of milk powder,well water and tap water were analyzed by the proposed method for their iron contents,the results obtained were in consistency with those obtained by AAS,with values of RSD′s (n=6) less than 2.5%.Recovery of the method was tested giving values of recovery in the range of 99%-102%.Apparent activation energy and constant of reaction rate of the catalytic reaction system were determined and the values are 34.56 kJ·mol-1 and 2.75×10-2s-1 respectively.