GC-MS in space research: decoding complex isothermal chromatograms recovered from space missions.
An analytical procedure is described to study GC-MS isothermal chromatograms simulating those recovered from space missions: in fact GC plays a predominant role in space missions devoted to characterizing the chemical composition of extra-terrestrial atmospheres. SIM (selected ion monitoring) detection was used for monitoring selected chemical classes: a simplified chromatogram can be obtained giving information on the chemical composition of the complex mixture. Since only isothermal GC chromatograms are allowed by flight constraints, a time axis transformation is required to make them homogeneous: i.e., constant retention increments for CH2 additions in terms of a homologous series. The order in the linearized chromatogram can be simply singled out with a chemometric approach based on the study of the Autocovariance Function (ACVF) computed on the digitized chromatogram: the plot of the experimental autocorrelation function (EACF) shows well-shaped peaks if constant interdistances are repeated in different regions of the chromatogram. The method was applied to standard mixtures representative of planetary atmospheres--hydrocarbons, nitriles and oxygenated compounds with between 3 and 12 carbon atoms--analyzed in flight simulating conditions. The coupling of the selectivity of SIM detection with the interpretation power of the EACF procedure proves to be a powerful tool for interpreting data recovered from space missions: the chemical composition of the mixture can be identified by handling the raw SIM chromatograms.
Pietrogrande
Maria Chiara
MC
Department of Chemistry, University of Ferrara, via L Borsari 46, 44100 Ferrara (Italy). mpc@unife.it
Zampolli
Maria Grazia
MG
Dondi
Francesco
F
D001331:Automation; D004784:Environmental Monitoring / Q000379:methods; D005118:Extraterrestrial Environment; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D013696:Temperature