Flow versus batch detection of radioactivity in column liquid chromatography

For column liquid chromatography, the precision of flow counting of radioactivity is compared with that of batch counting. Theoretical derivations are presented to show the decrease of precision in flow counting as a function of the sample count rate, the background count rate, and the residence time in the detector cell. A long residence time in the detector cell enhances the precision of the results, but this time can only be increased at the expense of either chromatographic resolution or retention time. The compromises which have to be made are treated quantitatively. Experimental results are shown which support the theoretical conclusions. The measurements were carried out with a GM counter, a NaI(TI) crystal and an organic solid scintillator. It is demonstrated that the selectivity of radiometric detection can be used to improve the accuracy of the analytical results