负热电离质谱技术在锇同位素测定中的应用

Application of Negative Thermal Ionization Mass Spectromery in Os Isotope Determination

本文用MAT－262质谱仪研究了负热电高质谱技术（N－TIMS）测定Os同位素组成的一些技术问题，首次采用样品与氧化剂一起点样等方法，配合通氧气（gasbleeding），显著地提高了电高效率，所获得的高于流强度明显高于文献值。获得的非放射成因Os同位素组成与国际著名实验室的数据一致，在样品量为0．2ng时仍获得了高精度的测试数据，明显优于现已发表的ICP－MS测试结果。可以测定多数地质样品中痕量（10－9～10－12）Os的同位素组成，为拓展我国Os同体素地球化学研究提供了高精度的测试手段。

Techniques on the determination of isotopic abundance of osrnium using negative thermal ionization mass spectrometry (N-TIMS)are discussed in this paper. Improvement on the method,for an example,loading samples together with oxidizer is proved to be useful. These methods coupled with gas bleeding can improve the ionization efficiency significantly. The stable osmium isotopic composition obtained in this experiment is concordant with those of literature. High precision data for 200 pg osmium samples is gotten,which means that the isotope compositions of trace Os (10-9~10-12)in geological samples is determinable. This technique is very important to the developement of osmium isotopic geochemistry in China.