We previously described a procedure for highly sensitive radiochromatography that is based on depositing fractions of the high-performance liquid chromatographic effluent on non-wetting film, concentrating them, transferring them to filter paper, generating autoradiographs of the paper on photographic film, and quantifying by densitometry. The work reported here included design of: a modified procedure for assaying non-polar compounds in which the transfer solvent was changed and silica gel thin-layer chromatography plates were substituted for the filter paper; a method for detecting tritium by adding scintillator to the filter paper before autoradiography and for distinguishing 14C and 3H by comparing autoradiographs with and without added scintillator. Then, to decrease the time for assaying the fractions, we tested two different kinds of gas radiation detectors, using the equivalent of an array of detectors working simultaneously. Since these detectors permitted a number of fractions to be assayed at the same time, the time each was assayed could be extended and/or the same number of fractions could be assayed more rapidly.
Following the successful application of these detector arrays, we designed a system concept for using an array of detectors for increasing the sensitivity of on-line, flow-through detection. Fractions of the effluent are passed through a series of detectors sequentially. The counting rates of each counter for each time interval are recorded. The results are summed electronically to reflect the position of each sample in the array. The same resolution is achieved as in flow-through detection, with comparable convenience but much enhanced sensitivity, since each fraction is assayed for a much longer time.