Problème particulier rencontré lors de la mesure par scintillation liquide des molécules marquées au carbone 14

The Chemical or the coloration quenching occurring in Iiquid scintillation counting is usually detected by the pulse-height shift [BAILLIE]. But an incomplete dissolution of the labelled compound in the scintiIIation medium, results in a low counting efficiency which cannot be detected by the above mentioned methods .It has been shown e.g., that the use of ethanol 94° instead of absolute alcohol reduces three times the counting efficiency of sucrose-¹⁴C dissolved in a 0.3 % aIcohoI/toIuene solvent.
Emphasis is laid on the fact that the experimenter has to choose the appropriate solvents in order to avoid any source of efficiency decrease which could not be detected by the routine methods of quenching evaluation.