40K measurement to determine the total potassium content

Total potassium concentrations has been determined measuring the 1461 keV gamma-rays emitted during the 40K decay. Using KCl salt set of 40K sources were prepared as standards and were used to characterize a NaI(Tl) γ-ray spectrometer. To test the procedure two unknown sources were used, for these 40K mass were determined as well as the specific activity. The rate of change between the mass of K and the net count rate under the 1461 keV photopeak is constant, allowing determining the mass of K measuring the γ-ray emitted during 40K decay. Specific activity was approximately 31 Bq/g being consistent with values reported in literature. (Author)