Measurement of carbon-14 and tritium in the effluent of a gas chromatography column.

Abstract

AbstractSeveral methods of measuring radioactivity in the effluent of a gas‐liquid chromatography (GLC) column are reviewed. If there is sufficient radioactivity in individual compounds to be measurable with acceptable precision in less than 15‐20 see, the effluent of a GLC column can be assayed for radioactivity during the course of an analysis. The effluent can be passed directly through a heated ionization chamber or proportional counter but both of these are some‐what sensitive to changes in the composition of the gas. The effluent can also be combusted to carbon dioxide and water, and the water then converted to HT for tritium assay. These gases can then be assayed in an ionization chamber, proportional counter or flow‐through scintillation counter at ambient temperature. The detector volume and gas flow rate can then be large so that changes in gas composition that occur during the course of an analysis are minimized. The gas flow is adjusted for optimal speed of response. Combustion trains have been developed that minimize memory effects in tritium assays that otherwise can cause difficulties. Convenient calibration methods are available for setting up the methods and for determining their efficiencies. When there is insufficient radioactivity in the sample to be measurable during a short time interval, the effluent can be fractionated, high boiling material in each fraction can be condensed out and assayed for radioactivity for longer periods. Automatic and quantitative fraction collecting devices have been developed for use with liquid scintillation counters that make this method of radioassay accurate as well as highly sensitive.