钍(Ⅳ)与偶氮溴膦-mB和溴化十四烷基吡啶在乙醇-水溶液中的显色反应及其分析应用

Colour Reaction of Thorium(Ⅳ)With Bromophosphonazo -mB and Tetradecylpyridinium Bromide in Ethanol-Aqueous Solution and Its Analytical Application

在pH1～2的酸性介质中,钍(Ⅳ)与偶氮溴膦-mB(BPAmB)形成最大吸收波长(λ_(max)位于686nm的蓝色络合物,摩尔吸光系数(ε)为8.27×10~4L·mol^(-1)·cm^(-1).在有少量乙醇存在的0.5～1.0 mol/L盐酸溶液中,钍(Ⅳ)能与BPAmB和溴化十四烷基吡啶形成更灵敏的三元络合物,最大吸收位于695nm,具有更大的对比度(△λ=135nm)和更高的灵敏度.ε值达1.41×10~5L·mol^(-1)·cm^(-1),是目前光度法测定钍(Ⅳ)灵敏度最高的显色反应之一,Th(Ⅳ)的浓度在0～800μg/L范围内遵守比尔定律.方法具有良好的选择性,此法用于岩矿中微量钍的测定,结果满意.

The colour reaction of thorium (Ⅳ ) with bromophosphonazo-mB (BPAmB) was studied. Itwas found that BPAmB reacts with thorium(Ⅳ) to form a blue binary complex in pH 1-2 acidic media,the apparent molar absorptivity was 8. 27×104L·mol-1·cm-1 at 686nm. In 0. 50-1.00 mol/Lhydrochloric acid solution containing a suitable amount of ethanol, a ternary micell complex of Th( Ⅳ )-BPAmB-tetradecylpyridinium bromide (TPB) with apparent molar absorptivity up to e = 1.41×105L·mol-1·cm-1 at 695 nm was formed which can be used for the spectrophotometric determination of thorium(Ⅳ) . Beer's law is obeyed in the range of 0-800Ug/L for Th(Ⅳ) . This method has good selectivityand high sensitivity. It has been applied to the determination of trace thorium in rock standard samples with satisfactory results.