Abstract
The apparatus used for measuring carbon-14 in a biological sample by wet combustion method was improved. In order to treat a few samples at the same time and to expel the evolved 14CO2 promptly, the decomposition flask was made as small as possible. A biological material, usually an organ itself or its homogenate equivalent to about 100 mg of wet sample, was placed in the decomposition vessel, and 15 ml of oxidizing agent, prepared from chromic trioxide (25 g), potassium iodate (5 g), phosphoric acid (d 1.7, 167 ml), and 60% fuming sulfuric acid (333 ml), was added by turning the reservoir 180°. The vessel was heated at 180-200° for 1 hr. 14CO2 was expelled with nitrogen and bubbled through a scintillator containing ethanolamine. This method was applicable not only to biological materials but also to such an insoluble sample as a resin. Recovery of carbon-14 was 98-100%. Scatter of measured values was examined with the same liver homogenate of a rat administered l-ephedrine[α-14C] and its standard deviation was 2.1%.
