GC-RAM™ - RGC Detector - Lablogic Systems Inc - #1

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Radioisotope Detector For Gas Chromatography The measure of radioactivity together with that of mass in gas chromatogra­phy effluents provides important and unique information. The GC-RAM can be used to détermine the spécifie ac-tivity of labeled compounds encoun-tered in pesticide residue studies, lipid research, steroid metabolism and other isotopic GC déterminations. Many high molecular weight compounds encountered in this work have rela-tively low volatility. Nevertheless, they can be chromatographed and their radioactivity determined on-line by continuons measurement using gas proportional counting. The Model 3 GC-RAM introduces the features of electronic control of count-ing gas flows as well as provision for an internai calibration source. Other new features include selectable analog output smoothing, seven différent data collection time bases, and analog background offset. THE PROBLEM: LOW VOLATILITY Condensation anywhere between the gas chromatograph and the exit of the radioactivity detector means loss of counts, loss of resolution, and ultimately counting tube contamination with increased background. On the other hand, excessive heating of the interconnecting tubing or the detector causes formation of tars and that too, results in a contaminated counting tube. In either case, even a system that initially appears to perform, soon becomes a continuing service problem. THE SOLUTION: OXIDATION/REDUCTION Central to the GC-RAM concept is a catalytic reactor closely positioned to the GC column, usually inside the oven. l4C-containing compounds are oxidized to l4CO, while 'H-containing compounds are initially converted to HTO which is subsequently reduced to HT gas. This way, there is no possibility of either condensation or tar formation and the same species is always counted at the same efficiency. IN/USAa Systems The Radiochromatography Company