Temperature effect in DIN- and pseudocumene-based liquid scintillation cocktails quenched with CCl4 and CH3NO2

A temperature-dependent effect is reported which concerns only DIN-based liquid scintillation cocktails when they are quenched with CCl4. The poor solubility of CCl4 at concentrations over 0.3% causes a slow decrease of the quenching parameter, which may require more than 25 days to reach steady values when the samples are kept at 16°C. The problem can be overcome by use of either nitromethane for quenching or the use of a non-DIN-based cocktail, which can otherwise lead to typical efficiency distortions of 2.5% for 14C or up to 41% for 55Fe.