Kalberer and Rutschmann (Helv, Chim, Act, 44 : 1956, 1961) described a method of estimating quantitatively C-14 compounds on a paper carrier, for example chromatograms. The sample is combusted in oxygen, the C14O2 produced being absorbed in ethanolamine solution and counted by liquid scintillation techniques. However, errors occur where there are deviations from their experimental conditions, such as in counting equipment or weight combusted, owing to differing concentrations of dissolved oxygen in counting solutions. Those errors can be eliminated by scrubbing the ethanolamine absorption solutions with nitrogen before they are mixed with the liquid scintillant. Furthermore, by this additional step, the range of weights combusted can be extended form 130 - 200 mg to 0-200 mg.