Inhibitory Kinetic Photometric Determination of 2,4-Dimethylphenol in Water

It was found that in phosphoric acid medium,the oxidation of fuchsin by hydrogen peroxide was strongly catalyzed by ruthenium(Ⅲ),leading to an enhancement of color fading of fuchsin.This indicator reaction was inhibited by the presence of 2,4-dimethylphenol.Based on these facts,the determination of traces of 2,4-dimethylphenol in water by inhibitory kinetic photometry was proposed.The optimized conditions found were as follows: ① amount of 2.0×10-4mol·L-1 fuchsin solution: 0.5 mL;② amount of 0.1 mol·L-1 phosphoric acid solution: 1.2 mL;③ amount of hydrogen peroxide solution (1+99): 0.5 mL;④ amount of 4.0 mg·L-1 Ru(Ⅲ) solution: 1.8 mL;⑤ temperature of reaction: 100 ℃;⑥ time of reaction: 10 min.Linear relationship between values of ΔA and mass concentration of 2,4-dimethylphenol was obtained in the range within 8.0 mg·L-1.Detection limit (3σ) of the method found was 3.49×10-4mg·L-1.The proposed method was applied to the determination of 2,4-dimethylphenol in environmental water,giving values of recovery ranged from 81.4% to 106.3%,and values of RSD's less than 6.0%.