By means of liquid scintillation spectrometry we investigated the counting efficiency of the samples containing toluene solution
of scintillator (PPO, butyl-PBD, PT) and 1-methyl[2−14C]imidazolidinone-2 adsorbed on the silicagel, depending on concentration of scintillator, mass of radioactive compound, and
mass of another nonactive compound introduced to samples as an impurity. For the sake of comparison the efficiency of counting
homogeneous samples and the ones with Ba14CO3 deposit was determined. It was found, that the efficiency of detection of a radioactive compound adsorbed on the silicagel
is conditioned by composition of adsorptive layer on the support surface.