Tubes and Scintillation Counters

The quantitative evaluation of paper chromatograms of radioactive substances by means of a Geiger-Miiller counter, a gas-flow proportional counter or a scintillation counter, has often been described. Detectors for radioactive radiation, with devices for automatic transport of a paper strip or of a two-dimensional chromatogram and for recording quantitative data, are commercially available. Such apparatus can be used for thin-layer chromatograms also if the layer is impregnated with a plastic emulsion and peeled off as a sheet [141, 618], Strip-scanners can be modifled for use with thin-layer chromatograms [484, 584]. 

Instruments are obtainable for direct quantitative evaluation of radioactive thin-layer chromatograms (Firms 13, 22, 44, 61, 99, 131a, 135). The Thin-layer scanner , constructed by Schulze and Wenzel [617] is illustrated in Fig. 85 two other counters are seen in Figs. 86 and 87. 

The sensitivity of these instruments for a particular radioisotope depends on the nature of the detector. Open methane gas-flow proportional counters give the highest count yields and have the additional 

Apparatus for recording the distribution of activity on thin-layer chromatograms. Fig. 85. Thin-Layer Scanner (Firm 44) Fig. 86. Model RSC-363, Deluxe Scanner (Firm 13) Fig. 87. Radio-Chromatograph (Firm 135) 

The influence of the adsorbent and of layer thickness on the count yield of three different isotopes is seen from Table 16. 

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