Effects of sodium salicylate on the determination of Lead-210/Bismuth-210 by Cerenkov counting

Due to the nature of Cerenkov radiation and instrumental limitations, detection efficiencies of 210Bi by Cerenkov counting are generally quite low (~15%). Sodium salicylate, acting as a wavelength shifter, has been used to improve the detection efficiency of Cerenkov photons. In this study, we found that the addition of sodium salicylate could significantly increase the counting efficiencies of 210Pb/210Bi in aqueous samples. Meanwhile, a sharp increase of the counting efficiency for the alphas from 210Po was also observed with the addition of high concentration of sodium salicylate, implying that scintillation light rather than Cerenkov photons from the alphas has been produced. Detailed studies about the effects of sodium salicylate on the counting of 210Pb, 210Bi and 210Po were conducted. At low concentration (< 0.5 mg g-1) of sodium salicylate, only a small increase in Cerenkov counting efficiency for 210Bi by the wavelength-shifting effect could be observed. Meanwhile, the counting efficiency for 210Bi at high concentration (> 1 mg g-1) of sodium salicylate would significantly increase due to the scintillation effect.