曙红B分光光度法测定痕量铋(Ⅲ)

Determination of trace bismuth(Ⅲ) by spectrophotometry with eosin B

在硫酸介质中,铋（Ⅲ）对碘酸钾氧化生物染料曙红B的褪色反应有强烈催化作用,据此建立了测定痕量铋（Ⅲ）的催化动力学方法。反应最优实验条件：在25 mL测定体积中,2.0×10^-3mol/L曙红B用量为1.2 mL,1.0×10^-2mol/L碘酸钾用量为1.5 mL,反应温度为90℃。在优化条件下,体系催化反应和非催化反应的吸光度变化值（ΔA）与铋（Ⅲ）质量浓度在0-0.18μg/mL范围内呈良好线性关系。方法检出限为8.04×10^-7g/L,表观速率常数为2.97×10^-4s^-1,表观活化能为36.74 kJ/mol。对0.06 g/mL Bi（Ⅲ）标准溶液进行11次平行测定,其相对标准偏差为2.7%。本法已用于水体中痕量铋（Ⅲ）的测定,相对标准偏差（n=6）为2.8%-3.2%,与原子吸收光谱法进行了对照,结果一致。

In sulphuric acid medium,bismuth（Ⅲ） had strong catalytic action on the fading reaction of biological dye eosin B oxidized by potassium iodate.Based on this,the catalytic kinetic determination of trace bismuth（Ⅲ） was established.The optimal experimental conditions were obtained： for 25 mL of solution,the dosage of eosin B（2.0×10^-3 mol/L） was 1.2 mL,the dosage of potassium iodate（1.0×10^-2 mol/L） was 1.5 mL and the reaction temperature was 90 ℃.The absorbency change（ΔA） of catalytic reaction and non-catalytic reaction showed good linear relationship with the mass concentration of bismuth（Ⅲ） in the range of 0-0.18 μg/mL.The detection limit of this method was 8.04×10^-7 g/L,the apparent reaction rate constant was 2.97×10^-4 s^-1,and the apparent activation energy was 36.74 kJ/mol.The standard solution of bismuth（Ⅲ） （0.06 g/mL） was determined for 11 times,and the relative standard deviation（RSD） was 2.7 %.The proposed method was applied to the determination of trace bismuth（Ⅲ） in water body with the relative standard deviation of 2.8 %-3.2 %,and the results were consistent with those obtained by atomic absorption spectrometry.