靛蓝褪色光度法测定锰的研究

Spectrophotometric determination of manganese based on fading reaction of indigo

在0．03～0．10 mol／L H2SO3介质中，Mn（Ⅵ）能氧化靛蓝使其显著褪色，且褪色的程度随锰量变化呈线性关系，据此建立了测定锰的光度分析新方法。探讨了褪色反应的最佳条件、共存离子对测定的干扰，并将方法应用于钢和铝合金中锰的测定。实验结果表明，在610nm波长处，非催化与催化反应的吸光度差值最大，且与Mn（Ⅵ）的质量浓度在0～2．0μg／mL范围内呈良好的线性关系。钢中常见金属元素不干扰测定，大量铁可以通过加入氟化钠溶液掩蔽。方法在用于测定钢样及铝合金中微量锰时，测定值与认定值相符，其相对标准偏差在1．1％～1．6％之间，回收率为99％～102％。

A novel spectrophotometric method for the determination of manganese was estabilished. It was based on the fact that the fading reaction of indigo could be oxidized by Mn（Ⅵ） in the medium of 0. 03--0. 10 mol/L H2804 , and the fading extent is linear with the amount of manganese. The optimum conditions of the fading reaction were examined along with the interference of coexisting ions on the determination. The method was applied to the determination of manganese in steel and atuminium alloy. It was indicated experimentally that, at 610 nm, the absorbency difference between non-catalytic reaction and catalytic reaction was the maximum and exhibited a good linear relationship with the mass concentration of manganese in the range of 0--2.0 μg/mL . Common metal elements in steel did not interfere with the determination, and a large amount of iron could be masked by adding sodium fluoride solution. For the determination of manganese in steel and aluminium alloy samples, the found values by the proposed method were consistent with the certified values, with RSDs（n=6） of 1.1%-- 1.6% and recoveries between 99% and 102%.