Inhibitory Catalytic Kinetic Photometric Determination of Trace Amount of EDTA in Canned Chestnuts

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%.