OBT Measurement of Vegetation by Mass Spectrometry and Radiometry

We carried out OBT (organically bound tritium) measurement by two different methods those are radiometry and mass spectrometry and compared the applicability of these methods for environmental tritium analysis. The dried grass sample was used for the experiments. To eliminate the exchangeable OBT, the sample was washed with tritium free water before analysis. Three times washing reduced the tritium activity in the labile sites below the detectable level.

In radiometry the sample was combusted to convert the OBT as well as other hydrogen isotopes to water and tritium activity in the water was measured by liquid scintillation counting (LSC). In mass spectrometry, the sample was kept in a glass container and ³He produced by tritium decay was measured by mass spectrometry. The results were in good agreement suggesting applicability of these methods for environmental tritium analysis. The mass spectrometry is more suitable for environmental tritium research because of a lower detection limit than that of the LSC.