钍-锌-茜素氨羧络合剂异多核络合物吸附伏安法测定痕量钍

Determination of Trace Thorium by Adsorptive Stripping Voltammetry with Thorium Ⅳ-Zinc Ⅱ-Alizarin Complexon Hetero-polynuclear Complex

在 0 .2mol LHAc NaAc(pH 4 .5 )缓冲溶液中钍与茜素氨羧络合剂 (ALC)、Zn2 + 形成电活性异多核络合物 ,吸附在静汞滴电极上 ,于 -0 .64V(vs.Ag AgCl)处产生一灵敏的阴极溶出峰 ,其峰高与钍浓度在 3 .0× 1 0 - 9～ 1 .5× 1 0 - 6 mol L范围内呈良好的线性关系 ,检出限为 1 .5× 1 0 - 9mol L。在含 6.0× 1 0 - 8mol LTh 的溶液中连续测定 1 0次RSD为 1 .85 %。对该体系的吸附伏安行为和电极反应机理进行了初步探讨 ,测定了该异多核络合物的组成。方法用于矿石和粘土中痕量钍的测定 。

A new reliable and sensitive method for the determination of the trace amounts of thorium by single-sweep stripping voltametry was proposed. The hetero-polynuclear complex of thorium-zinc-alizarin complexon was absorbed at a static mercury electrode in the buffer solution(pH 4.5) of 0.2 mol/L acetate and a sensitive cathodic stripping peak appeared at -0.64 V (vs. Ag/AgCl). The peak height of the hetero-polynuclear complex was proportional to the concentration of Th? in the range of 3.0×10 -9～1.5×10 -6 mol/L. The detection limit was found to be 1.5×10 -9 mol/L with 3 min of accumulation time and ten determinations of 6.0×10 -8 mol/L Th? gave a relative standard deviation of 1.9%. The molar ratio of each component in the hetero-polynuclear complex was estimated as n Th?∶n Zn(II)∶n ALC=1∶1∶2 by simplex method and continuous variation method. The properties of the adsorptive stripping peak and the electrode reaction mechanism were also discussed in detail. The method has been applied to the determination of trace amounts of Th? in the ore and clay samples with satisfactory results.