Spectrophotometric Determination of Fe(Ⅲ) by Its Reaction with Anthocyanin and Cetyl Trimethyl Ammonium Bromide

It was found that a colored complex of Fe(Ⅲ) with anthocyanin in the presence of CTMAB, was formed in an acetate buffer solution, having its absorption maximum at the wavelength of 620 nm.Based on this reaction, a spectrophotometric method for determination of Fe(Ⅲ) was proposed. The optimized conditions found were as follows: ① amount of 1.0 mol·L-1 HOAc-NaOAc buffer solution of pH 4.7: 3 mL; ② amount of 3.5 g·L-1 CTMAB solution: 3 mL; ③ amount of anthocyanin solution: 7 mL; ④ temperature of reaction: 50 ℃; ⑤ time of reaction: 5min. Linear relationship between values of absorbance and mass concentration of Fe(Ⅲ) was obtained in the range of 4.0-40 mg·L-1, with detection limit (3s/k) of 0.28 mg·L-1 and lower limit of determination (10s/k) of 0.92 mg·L-1.The proposed method was applied to the analysis of a rock standard sample (super mafic rocks DZE-2) giving results in consistency with the certified value, with RSD (n=12) of 1.9%.