FID radiochromatograph GC-RAM™

mass detector

The measurement of radioactivity in gas chromatography effluents offers more challenge than might be expected; many radio-labelled compounds encountered in pesticide residues etc. have high molecular weights and relatively low volatility. Gas proportional counting, the most practical method for continuous measurements of small amounts of these materials, can be nearly 100% efficient, yet its application raises practical problems. Low volatility is at the heart of these problems. Condensation between the GC and the radioactivity detector means loss of counts, loss of resolution, increased background and ultimately counting tube contamination. Excessive heating of the tubing and detector causes formation of tars, the resulting problems are similar. In either case, even a system that initially appears to perform soon becomes a continuing service problem. Placing these considerations foremost, the GC-RAM has been developed to eliminate them. Miniature Reactor Central to the GC-RAM concept is a catalytic reactor closely positioned to the GC column inside the GC oven. 14C containing compounds within the GC eluent are converted to 14CO2 while 3H containing compounds are first converted to 1H3HO which is subsequently reduced to 1H3H gas. That way, there is almost no possibility of condensation or tar formation. Of course, a splitter is required prior to the catalyst chamber if an FID or other mass detector is in use.