Counting of weak β-emitters in bacterial cells by means of the liquid scintillation method

Abstract

Liquid scintillation counting has been used to determine the C 14 and S 35 radioactivity of bacterial cells. A simple method for incorporating the cell material into the scintillation solution is described. This method involves the digestion of the cells with formamide and permits the incorporation of up to 10–11 mg cells (determined as dry solids) into 15 ml of a scintillation solution consisting of 10 ml 0.3% PPO in toluene and 5 ml ethanol. With smaller amounts of cells, viz., 6–7 mg, a simple autolysis of the cells at 60°C was found to be sufficient to bring the cell material into the scintillation solution. Various compositions of the scintillation solutions were investigated with respect to the counting efficiency of C 14 and S 35 in bacterial cells.