Gas chromatography of Titan's 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, is the use of microcolumns packed with carbon molecular sieve. The differential adsorption enthalpies are determined from the variation of retention volume with temperature. A linear variation with the polarisability of solutes is obtained and the relative retentions are similar to the adsorptions observed on graphitized carbon black. Two columns having different porosities are compared with respect to efficiency, resolution and detection limit. They all provide high efficiency, fast analysis and a detection limit of CO in N-2 suitable for the quantification of Titan's atmosphere composition. This detection limit is also studied with a vacuum column outlet using a mass spectrometer under conditions close to those of the flight instrument of the Huygens probe.