Separation and subsequent determination of low radioactivity levels of radium by extraction scintillation

A method is developed for separation and subsequent determination of low 226Ra levels based on its extraction efficiency by various organic extractants followed by direct interaction with mixed scintillation cocktail (SC) in toluene as the most suitable solvent. Three organic extractants including Tricaprylmethyleammonium chloride (Aliquat-336), triphenylphosphine sulphide (TPPS) and tri-n-octylphosphine oxide (TOPO) are individually embedded in 1-phenyl,4-phenyloxazole (PPO) as a primary scintillator and 1,4-di-2-(4-methyl, 5-phenyl oxazoyl) benzene (POPOP) as a second scintillator. Different parameters affecting the extraction process including shaking time, type and concentration of extractant, aqueous/organic volume ratio as well as various levels of 226Ra are individually investigated. Based on the optimized condition, it was found that the extraction of 226Ra by Aliquat-336 is highly selective with efficient separation capability from 133Ba, which is necessary to determine the yield and recovery of 226Ra in related measurements. The combination of extraction with direct scintillation processes is mainly elaborated to overcome the heterogeneity problem and hence the slow scintillation rate that often exists in conventional liquid scintillation counting especially with low radioactivity levels.