RUSSIAN DOLL TYPE CRYOGENIC TRAPS - IMPROVED DESIGN AND ISOTOPE-SEPARATION EFFECTS

An improved cryogenic trap for removing micromole quantities of conden sables from gas mixtures is described. It is based on the so-called Ru ssian doll design, with which extraordinary trapping efficiencies at n ow rates of up to 10 L/min are obtained, The active element consists o f one or more nested glass fiber thimbles, Despite the large fiber are a, quantitative retrieval of condensed CO2 is obtained, The new design is demountable and incorporates a heat exchange section; trapping eff iciency depends little on the level of coolant, as has been tested for CO2. When fractionation is induced by incomplete trapping, a small is otopic enrichment in C-13 occurs, It also has been discovered that whe n He is used as carrier gas, a gas chromatographic effect for CO occur s in Russian doll traps, accompanied by a large isotope separation, in which the elution sequence corresponds to the vapor pressure ratios o f the isotopomers.