OPTIMIZING THE PYROLYSIS TEMPERATURE OF TMSH THERMOCHEMOLYSIS FOR USE IN GC-MS BIOSIGNATURE DETECTION

The Sample Analysis at Mars (SAM) instrument aboard the Curiosity rover uses gas chromatography-mass spectrometry (GC-MS) to search for organic compounds in extraterrestrial environments. Nucleotides and fatty acids are examples of organic compounds that could potentially be considered biosignatures if detected in these environments. SAM contains the thermochemolysis reagent TMAH (tetramethylammonium hydroxide) to greatly increase the yield of fatty acid methyl esters in Mars samples in comparison to direct pyrolysis. However, TMAH degrades the GC column at a rapid rate, producing molecules that overwhelm the detector and make product identification difficult. The methylation reagent TMSH (trimethylsulfonium hydroxide) works via a similar mechanism to TMAH, but can achieve methylation at lower temperatures, potentially resulting in less column degradation. Here, we assess the utility of TMSH as a potential methylation reagent by determining the optimal pyrolysis temperature for use with TMSH. Thermochemolysis reactions of individual nucleotides, as well as a mixture of nucleotides and fatty acids in TMSH were analyzed at pyrolysis temperatures of 350^o, 400^o, 500^o, and 600^oC. Results show that more methylated nucleotide derivatives were consistently detected at 500^o and 600^oC, although more tailing occurred at 600^oC. Optimizing the utility of TMSH in this way will be crucial for further experiments to determine its potential for use in future space missions