A practical method for resolution of two β-emitting radionuclides by liquid scintillation counting

Abstract

A practical method for resolution of mixtures of two β-emitting radionuclides is described utilizing liquid scintillation counting procedures which combine simplicity of quench correction with the reliability of the “Discriminator ratio” method of double-label counting. A channel is set for each radionuclide, allowing 10 per cent overlap of the lower energy member into the channel set for the higher energy member, and quench correction standards and experimental samples are counted with and without an external standard. Simultaneous equation solutions are used which make optimal use of channels ratio data available by direct print-out. If R A and R B equal net cpm in channels A and B, R a and R b equal net cpm for radionuclides a and b, and F a ∼ and the channels ratio A B for radionuclides a and b, and R a = ( F b R B − R A / ( F a F b − 1) and R b = ( F a R A − R B )/ F a F b − 1). Values for F and counting efficiency (to convert cpm to dpm), as functions of the channels ratio A B for the external standard, amy graph made using counting data for the graphically derived from the quench correction standtards. quench correction standards. Absence of restrictions and ease of adaptation make the method applicable to any pair of β-emitting radionuclides sufficientlly different diffrecent in Energy to be accurately resolved; this can be determined from a plot of per cent error in resolution of each radionuclide as a function of the ratio of the amounts of each member present in the mixture.