Quench correction in liquid scintillation counting by a combined internal standard-samples channels ratio technique

Abstract

A well-known problem in liquid scintillation counting (LSC) is that radioactivity cannot be measured with 100% efficiency, e.g., due to ''quenching'', which thus needs be corrected for. Three methods (viz., those of internal standard (IS), samples channels ratio (SCR), and external standard channels ratio (ESCR) are in common use to accomplish quench correction. None of these methods is ideal. This paper shows that a combination of the IS and SCR methods (IS-SCR) ameliorates the major disadvantages of both techniques and the disadvantage of the SCR technique at low count rates have been eliminated in the IS-SCR method, which also has a low volume dependence compared to the IS and ESCR methods. The IS-SCR method is not affected by time-dependent diffusion of solutes and solvents into the walls of plastic counting vials, which is a major drawback of the ESCR technique. Used with a simple linear regression technique, the IS-SCR quench curves may be linearized over wide ranges of efficiencies. In view of the wide-spread application of LSC, the IS-SCR technique is therefore likely to be useful to many investigators. 2 figures, 2 tables.