GC-RAM™ - RGC Detector
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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 dͩtermine the spcifie ac-tivity of labeled compounds encoun-tered in pesticide residue studies, lipid research, steroid metabolism and other isotopic GC dterminations. 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 diff驩rent 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

OX1 DATION ()R REDUCTION to HT prior to the point of P-10 entry. A splitter is place! at the exil of the GC column so that part of the effllient passes to the mass dtecter and part to the reactor tubes. The reactor op驩rtes in the range of 750° C; it is especially robust and is rated at near 900° C for continuous use. Prcise temp⩩rature control minimizes tailing; reactor temprature is maintained constant to ± 0.25° C. One reactor tube is provided for oxidation and a second, operated in s魩ries with the first, is used for rduction. HIGH SENSITIVITY Thorough attention to dtail has resulted in...