0.500 0 g试样溶于硝酸及数滴盐酸中,加入硫酸(1+1) 4 mL冒烟,冷却后用3.0 mol·L-1氢氧化钠溶液调节试液酸度至pH 2.0~2.5,将试液以0.5~1.0 mL·min-1流速通过阴离子交换树脂柱.试样中钍(Ⅳ)与铀(Ⅵ)与硫酸根形成络阴离子吸附在树脂上,用0.01 mol·L-1硫酸(20 mL)淋洗树脂,使钍及铀与钆等其他元素分离,弃去洗出液,改用6.0 mol·L-1盐酸作洗提液,流速上同.弃去最先流出的7 mL洗出液,收集之后流出的18 mL洗出液于一小烧杯中,其中含有试样中的钍,铀仍留在树脂上.将溶液蒸至近干,用1.0 mol·L-1硝酸溶解残渣并移入5 mL容量瓶中,用此硝酸溶液洗涤并定容.此溶液供电感耦合等离子体原子发射光谱法(ICP-AES)测定,对仪器的最佳工作条件及钍的分析条件作了较详细的分析.方法的测定下限为0.2 μg·g-1,进行加标回收试验及精密度试验,相对标准偏差结果(n=6)为9.6%,平均回收率为105%.

0.500 0 g of the sample was dissolved in HNO3 with addition of several drops of HCl,and then fumed with 4 mL of H2SO4(1+1).After cooling,acidity of the solution was adjusted to pH 2.0-2.5 with 3.0 mol·L-1 NaOH solution.Thorium,together with the matrix uranium were adsorbed on the anion exchange resin column in the form of anionic complex with SO2-4 anion,and separated from Gd(Ⅲ) and other co-existing cation by elution with 0.01 mol·L-1 H2SO4 (20 mL) at a flow-rate of 0.5-1.0 mL·min-1.The eluate was rejected.6.0 mol·L-1 HCl was then used as eluant and passed through the resin column at same flow-rate.The first 7 mL of the eluate were discarded,and the next 18 mL of the eluate,which contained the thorium,were collected in a small beaker and evaporated to near dryness.The residue in the beaker was taken up with 1.0 mol·L-1 HNO3 and diluted to 5 mL with the same HNO3 solution in a volumetric flask,and ready to be used for ICP-AES determination.Optimum working conditions of the instrument and for the determination were described in detail.Detection limit of the method was found to be 0.2 μg·g-1.Values of RSD (n=6) and av.recovery were found to be 9.6% and 105% respectively.