Optimization of 14C LSC measurement using CO2 absorption technique

Liquid Scintillation Counting (LSC) is the most commonly used technique for quantification of 14C in the environmental samples. An optimization study was carried out for the analysis of 14C with the direct carbon dioxide absorption method using LSC. The absorption capacity of CO2 in varying amounts of CO2 absorber Carbo-Sorb E to Permafluor scintillation cocktail volumes is found to be 5.33 ± 0.053 mmol/mL of Carbo-Sorb E. The optimum volume ratio of Carbo-Sorb E to Permafluor scintillation cocktail is found to be 1:1 based on the minimum detection activity (MDA) values. The effect of CO2 loading in the optimized absorption mixture shows that with an increasing CO2 amount (up to saturation) there is an increase in tSIE values which is due to an increase of Compton scattering effect in the CO2 loaded samples. The region of interest (ROI) for 14C measurement is found to be 10–96 keV based on the figure of merit values and the efficiency for detecting 14C is 83.45 % in the optimized ROI window.

Rapid determination of gross alpha/beta activity in milk using liquid scintilation counter technique

Rapid determination of gross alpha and beta emitters in milk by liquid scintillation counter is discussed. This method is based on direct addition of different types of milk into scintillation cocktail and therefore it is very promising for fast determination of alpha/beta activity due to direct alpha and beta separation, measurement in close 4p geometry and without sample treatment. The selected group of radionuclides was chosen with the respect to military significance, radio-toxicity, and possibility of potential misuse. As model radionuclides 241Am, 239Pu, and 90Sr were selected. The Liquid Scintilation Counter Hidex 300 SL equipped with triple-double-coincidence-ratio technique was used for sample measurement. The aim of the work was focused on comparison of different cocktails produced by Hidex and Perkin Elmer, choosing the best cocktail based on our measurement results and adjustment of its appropriate volume. Furthermore, the optimization of ratio between the volume of scintillation cocktail and the volume of urine was investigated with the respect to the model radionuclides. According to the obtained results, the efficiency for alpha emitters was greater than 85% and for beta, greater than 95%. The obtained results allowed this method to be used for rapid determination of gross alpha/beta activity in cases where time is an essence, such as first responders or mass-scale samples, where ordinary means suffer from lack of capacity or simply collapse under the onslaught.