高碘酸钾氧化肼黄褪色催化动力学光度法测定铁

在硫酸介质中,高碘酸钾能氧化肼黄褪色使其吸光度下降,而铁的加入能明显地催化这一反应,其催化程度与加入铁Ⅲ的浓度有关,据此建立了肼黄褪色催化动力学光度法测定痕量铁Ⅲ的方法。考察了不同试验条件对催化反应灵敏度的影响,得到了最佳试验条件:4.0 mL硫酸,0.9 mL高碘酸钾溶液,1.5 mL肼黄溶液,反应温度为100 ℃,反应时间为 9 min。并考察了Na⁺、K⁺、Cl^-、SO₄^2-等多种常见金属和非金属离子对反应的影响,发现大部分常见离子对测定无干扰或者干扰较小。在最佳测定条件,测得体系的最大吸收峰为427 nm,该催化反应的速率常数为9.8×10^-4/s,表观活化能为23.63 kJ/mol。铁的质量浓度在2.4～40 μg/L范围内校准曲线呈线性,相关系数r=0.998 7;方法检出限为2.4×10^-7 g/L。实验方法用于测定自然水中铁,结果的相对标准偏差(RSD,n=6)为1.7%～2.4%;测定结果与火焰原子吸收法测定结果基本一致。

Determination of iron by catalytic kinetic spectrophotometry based on the oxidization fading reaction of hydrazine yellow with potassium periodate

The potassium periodate could oxidize the hydrazine yellow in sulfuric acid medium, leading to the decrease of absorbance. The addition of iron (III) could obviously catalyze this reaction. Moreover, the catalytic extent was related to the concentration of added iron (III). Based on this, the determination method of trace iron (III) by hydrazine yellow fading catalytic kinetic spectrophotometry was established. The effect of different testing conditions on sensitivity of catalytic reaction was investigated. The optimal experimental conditions were obtained: 4.0 mL of sulfuric acid; 0.9 mL of potassium periodate solution; 1.5 mL of hydrazine yellow solution; the reaction temperature of 100 ℃; the reaction time of 9 min. In addition, the influence of several common metal and nonmetal ions on the reaction was investigated, including Na⁺, K⁺, Cl^- and SO₄^2-. It was found that most common ions had no or little interference with the determination. Under the optimal determination conditions, the maximum absorption peak of system was 427 nm, the catalytic reaction rate constant was 9.8×10^-4/s, and the apparent activation energy was 23.63 kJ/mol. The calibration curve was linear when the mass concentration of iron was in range of 2.4-40 μg/L, and the correlation coefficient was r=0.998 7. The detection limit of method was 2.4×10^-7 g/L. The proposed method was applied to the determination of iron in natural water. The relative standard deviations (RSD, n=6) were between 1.7% and 2.4%. The found results were consistent with those obtained by flame atomic absorption method.