Gas chromatography for in situ analysis of a cometary nucleus II. Analysisof permanent gases and light hydrocarbons with a carbon molecular sieve porous layer open tubular column

Considering the severe constraints of space instrumentation, a great improv ement for the in situ gas chromatographic (GC) determination of permanent a nd noble gases in a cometary nucleus is the use of a new carbon molecular s ieve porous layer open tubular (PLOT) column called Carbobond. No exhaustiv e data dealing with this column being available, studies were carried out t o entirely characterize its analytical performances, especially when used u nder the operating conditions of the cometary sampling and composition (COS AC) experiment of the European Space Agency (ESA) Rosetta space mission to be launched in 2003 for a rendezvous with comet 46 P/Wirtanen in 2011. The high efficiency and speed of analysis of this column at both atmospheric an d vacuum outlet column pressure is demonstrated, and the kinetic mass trans fer contribution of this carbon molecular sieve adsorbent is calculated. Be sides, differential adsorption enthalpies of several gases and light hydroc arbons were determined from the variation of retention volume with temperat ure. The data indicate close adsorption behaviors on the Carbobond porous l ayer adsorbent and on the carbon molecular sieve Carboxen support used to p repare the packed columns. Moreover, taking into account the in situ operat ing conditions of the experiment, a study of two columns with different por ous layer thicknesses allowed one to optimize the separation of the target components and to select the column parameters compatible with the instrume nt constraints. Comparison with columns of similar selectivity shows that t hese capillary columns are the first ones able to perform the same work as the packed and micro-packed columns dedicated to the separation of this ran ge of compounds in GC space exploration. (C) 2000 Elsevier Science B.V. All rights reserved.