在硫酸介质中,Fe(Ⅲ)对过氧化氢氧化中性红的褪色反应具有强的催化作用,EDTA对上述指示反应具有灵敏的阻抑作用,从而提出了一种阻抑催化动力学光度法测定板栗罐头中痕量EDTA的方法。优化的试验条件如下:① 过氧化氢用量为1.0 mL;② 0.1 g·L-1中性红溶液用量1.0 mL;③ 50.0 mg·L-1 Fe(Ⅲ)溶液用量为0.12 mL;④ 反应温度为沸水浴;⑤ 反应时间为10 min。EDTA的质量浓度在900 μg·L-1以内与ΔA呈线性关系,检出限(3s/k)为8 μg·L-1。方法用于板栗罐头中EDTA的测定,测定值的相对标准偏差(n=6)小于3.0%,加标回收率为93.0%~96.0%。

It was found that in H2SO4 medium, the oxidation of neutral red by hydrogen peroxide was strongly catalyzed by Fe(Ⅲ), leading to an enhancement of color fading of neutral red. This indicative reaction was inhibited by the presence of EDTA. Based on these facts, the determination of traces of EDTA in canned chestnuts by inhibitory catalytic kinetic photometry was proposed. The optimized conditions found were as follows: ① amount of hydrogen peroxide solution: 1.0 mL; ② amount of 0.1 g·L-1 neutral red solution: 1.0 mL; ③ amount of 50.0 mg·L-1 Fe(Ⅲ) solution: 0.12 mL; ④ temperature of reaction: boiling water bath; ⑤ time of reaction: 10 min. Linear relationship between values of ΔA and mass concentration of EDTA was obtained in the range within 900 μg·L-1. Detection limit (3s/k) of the method found was 8 μg·L-1. The proposed method was applied to the determination of EDTA in canned chestnuts. Recovery was tested by addition of standard solution to the chestnut sample, giving values of recovery ranged from 93.0%-96.0%, and values of RSD (n=6) less than 3.0%.