Carius管直接蒸馏快速分离锇方法的改进

蒸馏法是Re-Os同位素测量体系从基质中分离Os的一种快捷方法,但装置繁琐,清洗工作量大,已成为限制其应用的瓶颈。文章对Carius管传统蒸馏装置进行了改进,利用橡胶滴头代替硅胶管和玻璃堵头自制Carius管直接蒸馏接口装置,简化了气体进出口管路,使用电蒸笼代替电热套,对蒸馏时间、样品溶液稀释倍数和吸收液体积等蒸馏条件进行了优化。改进后的装置升温速度、稳定性和简便性得到提高,简化了实验器皿,有利于降低空白,实现在较小操作空间内大批量样品的同时处理。Carius管直接蒸馏实验结果表明,Os的回收率可达86.7%～95.2%。在长时间(2 h)蒸馏条件下,Os回收率比传统蒸馏瓶法高约41%。针对不同样品类型和测试仪器,可选择相应的蒸馏条件,有效压缩了样品处理时间,提高了测量计数。对Re-Os定年标准物质GBW 04436(JDC)测定5次的模式年龄为(139.5±1.9)Ma～(142.0±2.1)Ma,标准物质GBW 04435(HLP)测定2次的模式年龄为(220±3.3)Ma～(223.0±3.2)Ma,分别与标准值(139.6±3.8)Ma和(221.4±5.6)Ma在不确定度范围内一致。改进后的Carius管直接蒸馏装置已应用于日常样品处理。

Improvements on the Separation Method of Osmium by Direct Distillation in Carius Tube

Distillation is a simple method for separating Os from the sample matrix. However, complicated apparatus and heavy cleaning work have been the major limitation to its application. In this paper, the Carius tube direct distillation apparatus was improved and simplified by using latex dripper to replace the silicone tube and glass end cap and an electric steamer to replace the electric jacket. The distillation time, dilution factor and volume of the trap solution were optimized. After the improvements, the heating rate, stability and simplicity of the apparatus were improved, the cleaning work was reduced significantly to obtain a lower blank level, and large batches of samples can be treated in a relatively small working space. The experimental results indicate that the Os recovery of this method ranges from 86.7% to 95.2%. After being distilled for 2 h, Os recovery of the Carius tube direct distillation was about 41% higher than that of the traditional distilling flask method. For different samples and testing instruments, corresponding distilling conditions can be chose to shorten the treating time and enhance the signal intensity. The dating results obtained from molybdenite reference materials GBW 04436 (JDC) and GBW 04435 (HLP) were (139.5±1.9) Ma -(142.0±2.1) Ma (n=5) and (220±3.3) Ma -(223.0±3.2) Ma (n=2), respectively, in good agreement with certified values of (139.6±3. 8) Ma for GBW 04436 and (221.4±5.6) Ma for GBW 04435. This method was applied as a routine method for Os separation.