There are a variety of tritium exchange reactions which can be used to label compounds with tritium. Three common techniques are described below.
Tritium Gas Exchange Using a Hydrogen Transfer Catalyst
Tritium gas exchange using a hydrogen transfer catalyst can be employed in labeling compounds such as carbohydrates, nucleosides, nucleotides, alkaloids, amino acids and compounds containing benzylic protons. This technique achieves specific activities of 1-50 Ci/mmol.
Tritium gas exchange using a hydrogen transfer catalyst includes the following:
- Exposure of your compound to the appropriate amount of carrier-free tritium gas and catalyst
- Complete removal of labile tritium
- Assay of the crude product for total activity
Exchange with Tritiated Water
Tritiated water in acidic, basic, or neutral solutions can be used to label compounds such as nucleotides, pyrimidines, and alkaloids. This tritium exchange technique usually achieves specific activities of 0.5-30 Ci/mmol.
Exchange with tritiated water includes the following:
- Reaction of your compound with the appropriate amount of tritiated solvent
- Complete removal of labile tritium
- Assay of crude product for total activity
Exposure to Tritium Gas
Labeling by exposure to tritium gas, known as the Wilzbach method, can be performed on some pharmaceutical and other complex compounds with satisfactory results. However, many compounds will suffer significant radiation-induced decomposition and achieve low specific activities. This method should be used only if the compound cannot be labeled using other less destructive methods.
Gas exposure tritium labeling includes the following:
- Exposure of your compound to 15 Ci of carrier-free tritium gas
- Complete removal of labile tritium
- Assay of the crude product for total activity