Studies of tritium labelling method utilizing microwave discharge activation of tritium gas

An improved method of tritium labelling utilizing double cavity microwave discharge activation of tritium gas is developed. The tritium labelling reaction apparatus consists of a closed vacuum system in which tritium gas can be cycled by a glass reciprocating pump. Two microwave generators are used to power the Evenson cavity and the McCarrol cavity to induce the tritium plasma separately. The tritium labelling reaction of the labelled substrate in the reaction area is initiated by microwave discharge activation of tritium gas. Dehalogenation of 8-BrcAMP and addition of 1-dehydrotestosterone by tritium atoms under the microwave discharge activation condition are studied for the synthesis of [8-3H]cAMP and [1,2-3H]testosterone with the high specific activities. The influence of a palladium catalyst on the microwave tritium labelling reaction and dehalogenation or addition of the starting materials are discussed. In order to increase the specific activities of the tritium labelled compounds, a technique of labelling one and the same sample by the repeated microwave labelling operation is introduced. Several tritium labelled compounds can be prepared simultaneously by this new method