Separation of carrier-free iodine from low-level iodine samples and accurate measurement of ultra-low-level 129I in microgram iodine target are essential but a bottleneck in geology and environment research using naturally produced 129I. This article presents a detection technique of accelerator mass spectrometry (AMS) for accurate determination of ultra-low-level 129I in carrier-free AgI-AgCl sputter targets. Copper instead of aluminum was selected as the suitable sample holder material to avoid the reaction of AgI-AgCl powder with aluminum. Niobium powder was selected as thermally and electrically conductive matrix to be mixed with AgI-AgCl powder, in order to obtain and maintain a stable and high iodine ion current intensity, as well as less memory effect and low background level of 129I. The most optimal ratio of the Nb matrix to the AgI-AgCl powder was found to be 5:1 by mass. The typical current of 127I5+ using AgI-AgCl targets with iodine content from 5 to 80 μg was measured to be 5 to 100 nA. Four-year AMS measurements of the 129I/127I ratios in standards of low iodine content and the machine blanks showed a good repeatability and stability.
|Journal||Journal of The American Society for Mass Spectrometry|
|Number of pages||9|
|Publication status||Published - 2015|
- Accelerator mass spectrometry
- AgI-AgCl target
- Low level measurement