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研究了测定铁的一种新指示反应，在稀硫酸介质中，痕量铁（Ⅲ）对高碘酸钾与过氧化氢协同氧化变色酸２Ｒ的褪色反应具有强烈催化作用，其反应的动力学条件，表观活化能Ｅ′＝１８９．８１ｋＪ／ｍｏｌ，表观反应速率常数Ｋ＝５．６７×１０－４／ｓ，半衰期ｔ１／２＝２０．３７ｍｉｎ。反应温度为９０℃，试验表明ｌｇＡ０／Ａ与Ｆｅ（Ⅲ）的浓度在３０～１００ｎｇ／２５ｍＬ范围内符合Ｂｅｒ定律，建立了催化动力学光度法测定痕量铁的新方法。方法的检测限为１．２５×１０－９ｇ／Ｌ，加入回收率在９７．０％～１０２％，应用于测定西洋参口服液、美国花旗参茶和天然矿泉水中铁的含量结果满意。
A new indicator reaction for the determination of iron has been studied. Trace iron (Ⅲ) has a strong catalytic effect on the fading reaction of potassium periodate and hydrogen peroxide in synergistic oxidation of chromotropic acid 2R in dilute sulfuric acid. The reaction kinetics The conditions, the apparent activation energy E ’= 189.81kJ / mol, the apparent reaction rate constant K = 5.67 × 10-4 / s, half-life t1 / 2 = 20.37min. The reaction temperature was 90 ℃. The results showed that the Ber law of lgA0 / A and Fe (Ⅲ) was in the range of 30 ~ 100ng / 25mL, and a new method for the determination of trace iron by catalytic kinetic spectrophotometry was established. The detection limit of this method was 1.25 × 10-9g / L with the recoveries of 97.0% ~ 102%. The method was applied to the determination of iron content in American ginseng oral liquid, American ginseng tea and natural mineral water with satisfactory results.