在乙酸盐缓冲溶液中,花青素与铁(Ⅲ)在溴化十六烷基三甲基铵(CTMAB)的存在下形成的有色络合物,其最大吸收波长为620 nm,据此提出了花青素-CTMAB体系分光光度法测定铁(Ⅲ)。优化的试验条件如下:① pH 4.7的1.0 mol·L-1乙酸-乙酸钠缓冲溶液用量为3 mL;② 3.5 g·L-1 CTMAB溶液用量为3 mL;③ 花青素溶液用量为7 mL;④ 反应温度为50 ℃;⑤ 反应时间为5 min。铁(Ⅲ)的质量浓度在4.0~40 mg·L-1范围内与吸光度呈线性关系,检出限(3s/k)为0.28 mg·L-1,测定下限(10s/k)为0.92 mg·L-1。方法应用于岩矿标准样品(超基性岩DZE-2)中铁(Ⅲ)的测定,测定值与认定值相符,测定值的相对标准偏差(n=12)为1.9%。

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%.