GAS-CHROMATOGRAPHY OF TITANS ATMOSPHERE .8. ANALYSIS OF PERMANENT GASES WITH CARBON MOLECULAR-SIEVE PACKED CAPILLARY COLUMNS

An alternative for an in situ GC analysis of permanent gases in Titan' s atmosphere, given the severe constraints on space instrumentation, i s the use of microcolumns packed with carbon molecular sieve. The diff erential adsorption enthalpies are determined from the variation of re tention volume with temperature. A linear variation with the polarisab ility of solutes is obtained and the relative retentions are similar t o the adsorptions observed on graphitized carbon black. Two columns ha ving different porosities are compared with respect to efficiency, res olution and detection limit. They all provide high efficiency, fast an alysis and a detection limit of CO in N-2 suitable for the quantificat ion of Titan's atmosphere composition. This detection limit is also st udied with a vacuum column outlet using a mass spectrometer under cond itions close to those of the flight instrument of the Huygens probe.