Biosignature Detection from Amino Acid Enantiomers with Portable Gas Chromatography Systems

Abstract

This paper presents developments in stationary phase coatings for microelectromechanical system gas chromatography (MEMS GC). Specifically, we present the coating of MEMS GC separation columns with a chiral stationary phase for the separation of amino acid enantiomers. Three commercial columns coated with chiral stationary phases from Restek were tested: Rt-βDEXm, Rt-βDEXsm, and Rt-βDEXsa. Four amino acid enantiomers (d- and l-) were tested with the 3 commercial columns: alanine (Ala), valine (Val), leucine (Leu), and aspartic acid (Asp). The Rt-βDEXsm column provided the best experimental performance with separation of d- and l-Ala and partial separation of d- and l-Asp. The resolution, Rs, values were 4.65 for the Ala enantiomers and 0.98 for the Asp enantiomers, respectively. The Rt-βDEXsm chiral stationary phase was dynamically coated on three 10-m-long microcolumns connected in series to investigate amino acid enantiomer separation. Successful separation of d- and l-Ala and partial separation of d- and l-Asp were observed with the microcolumns. The Rs values from the chiral-stationary-phase-coated microcolumns were 1.21 and 0.553 for the Ala and Asp enantiomers, respectively. The chromatographically separated amino acid enantiomers were detected by the MAss Spectrometer for Planetary EXploration (MASPEX), a spaceflight mass spectrometer. Future work is required for improving the MEMS GC separation column performance consisting of testing static versus dynamic coating methods and more rigorous investigation of the stationary phase coating thickness. A discussion is provided on future work for the development of an MEMS GC suite targeting broad analyte selectivity for future space science missions.