Use of internal scintillation standards in heterogeneous counting systems

Abstract

In the course of determining the distribution of H 3 and C 14 in samples of rat liver glycogen-glucose by the procedure of Bloom (1), which utilizes homogeneous counting systems, it became desirable to check the H 3 content of positions 2–6 of the liver hexose by an independent method. The procedure attempted consisted of oxidation of the hexose to potassium gluconate (2), suspension of the salt in a thixotropic gel powder phosphor system (TGP), and assay for H 3 and C 14 in accord with the discriminator ratio method of Okita et al. (3). In order to compare the results obtained from the assay of potassium gluconate in TGP with those obtained from the hexose degradation procedure (1), the relative H 3 and C 14 efficiencies of the individual systems were evaluated using toluene-H 3 and toluene-C 14 as the internal scintillation standards (ISS). The data obtained by the two procedures proved mutually incompatible. The discrepancy has been shown to be related to the ISS used to evaluate the relative efficiencies. In the heterogeneous TGP phosphor system the added ISS makes up the solvent phase, which has strikingly different counting characteristics as compared to that of the particulate phase of the system.