Cryptic “photon” quenching in dioxane-based liquid scintillation mixtures

Abstract

Dioxane-based scintillation mixtures containing β-emitting radioisotopes show a decreased efficiency under the following conditions: low water concentration in the sample, the presence of some metal ions, e.g., Ca2+, Mg2+, and certain3H- and 14C-labeled compounds, e.g., nucleotides. If only one of the preconditions was not fulfilled, the effect disappeared. There is no visible sign of any form of sample inhomogeneity, and the composition of the scintillation sample gives no reason to suppose that a special sort of quenching would occur. In addition, no commonly used standardization method, such as external standard channels ratio, internal standard, or sample channels ratio could be used to detect this sort of quenching, to say nothing of correcting for it. A further analysis shows that the decreased count rate has to be explained by a special sort of “photon” quenching. The so-called “double ratio plot” proposed by Bush ((1968) Int. J. Appl. Radiat. Isotop.19, 447–452) to provide an indication of sample heterogeneity failed to indicate this sort of photon quenching.