Unveiling the Nitrogen Chemistry of Titan with the Dragonfly Mass Spectrometer: Experimental Focus on Amines and Amides

Abstract

The Dragonfly mission payload includes the Dragonfly Mass Spectrometer (DraMS) instrument, which operates in both gas chromatography–mass spectrometry (GCMS) and laser desorption mass spectrometry (LDMS) analysis modes. DraMS will investigate Titan chemistry at geologically diverse locations. Titan uniquely offers direct access to abundant, complex, carbon- and nitrogen-rich chemistry on the surface of a water-ice-dominated ocean world. Amino and amide functional groups, if both present, would be witnesses of redox conditions in the surface environment. An enantiomeric excess in those compounds could help discriminate the chemical or biological origins of these molecules. In this study, we first investigated a wide range of amines and amides (primary, secondary, tertiary, aliphatic, aromatic, branched, and linear moieties) using DraMS-like GCMS protocols, with sample volatilization via both pyrolysis and wet chemistry (derivatization with dimethylformamide dimethyl acetal─DMF-DMA). We determined the general patterns of this derivatization according to the chemical families: dimethylformamidination of the primary amines and amides; methylation, formylation, and dimethoxymethylation of the secondary amines; and lack of derivatization of the secondary amides. The minor coproducts were also identified for each chemical family, to help strict identification of molecules in a Titan GCMS spectrum. The limits of detection and quantification showed that N-species could be detected in the range of tens of fmol to hundreds of pmol. Out of the six chiral amines and amides investigated, five were enantiomerically resolved. We also performed LDMS measurements on a subset of compounds, amines─aliphatic and aromatic─and an amide, and their detection and identification demonstrated the complementarity of LDMS and GCMS modes. Altogether, our results demonstrate the application of DraMS to characterize the expected wide diversity of N-containing compounds of interest at Titan’s surface.