Low-Level Measurement with a Noble Gas Mass Spectrometer for Organically Bound Tritium in Environmental Samples

We developed an analytical method for organically bound ³H (OBT) in biological environmental samples by using noble gas mass spectrometry of ³He produced from ³H. Three environmental samples with background level OBT concentrations were analyzed, and the results agreed well with those by the conventional liquid scintillation counting of electrolyzed combustion water of the samples. This showed that the method is practical and effective.

We also developed an analytical method for non-exchangeable OBT as a combination of pre-treatment of dried samples with free water ³H and our newly developed analytical method for OBT. The repeated analysis of a grass sample with moderate ³H concentration had smaller variance of results for non-exchangeable OBT than for OBT. The sum of non-exchangeable and exchangeable OBT agreed well with OBT measured in the samples. The developed method was successfully applied to terrestrial and marine environmental samples with background ³H levels.