铌钼杂多酸-结晶紫缔合物体系光度法测定痕量铌

Spectrophotometric Determination of Trace Niobium as Ion-associated Complex of Molybdoniobate and Crystal Violet

在聚乙烯醇存在下,铌与钼酸铵形成铌钼杂多酸阴离子,与结晶紫阳离子形成离子缔合物,其最大吸收波长为640nm,表观摩尔吸光系数ε=8.52×10~5,线性范围0～5pzNb/25ml。考察了37种共存离子的影响,大多数元素不干扰测定,方法灵敏度高,选择性好,操作简便,用于合金钢中铌的测定,结果满意。

The ion-associated complex of molybdoniobate heteropoly acid and crystal violet in the presence of polyvinyl alcohol is used as the basis for a spectrophotometric method for the determination of niobium(V). The optimum conditions for formation of the ion-associated complex are described. The molar absorptivity of the complex is 8.52×105L· mol-1· cm-1 at 640 nm. The system conforms to Beer's law in the range for niobium(V) 0 to 5ng/ 25ml for a 5mm cell. Tolerance limits have been shown for 37 foreign ions. The system was applied to the determination of niobium in steel.