Looking for Clues of Extant or Extinct Life on Mars: GC-MS Analysis of Amino Acid Enantiomers using N,N-Dimethylformamide Dimethylacetal (DMF-DMA): (Abstracts from the Eighth European Workshop on Astrobiology, 1-3 September 2008, Neuchâtel, Switzerland)

International audience; In the frame of the future MOMA experiment of the European Exomars 2013 space mission aimed at finding traces of life, our work deals with the optimization of the derivatization parameters of chiral organic molecules such as amino acids using N,N- Dimethylformamide Dimethylacetal (DMF-DMA) as derivatizing agent. In order to optimize the chiral derivatization, within space operating conditions, several parameters such as temperature (90 to 170C) and reaction time (30 s to 60 min) have been studied using a Chirasil-Dex capillary column for the enantiomeric separation. This technique performed in one-step reaction is space compatible and allows to identify 18 out the 20 proteogenic amino acids and to separate enantiomerically 11 out of the 19 ones (glycine being non-chiral) with a single column using -cyclodextrin stationary phase. In a second step, the racemization rate, which varies according to the nature of the amino acid, has been studied under the optimal conditions of derivatization. Racemization is all the more important since temperature is the key factor of this phenomenon. The higher the temperature, the faster will the racemization be. Thus, for example when only D-form of threonine is injected, the D-enantiomeric excess drops from 100 to 28 when the temperature used for the derivatisation is increased from 70 to 150C, this drop being respectively 72 and 60 at 90 and 120C. The optimal heating time of the derivatization reaction has been also determined allowing high derivatization efficiency and low rate of racemization of the enantiomers and destruction of the amino acids. Quantitative studies were also carried out: linearity studies and the measurement of the limit of detection (LOD) show that the proposed method is suitable for a quantitative determination of enantiomers of several amino acids within a limit of detection (lower than the ppb level) compatible with that found in Martian meteorites.