Removing perchlorate from samples to facilitate organics detection by pyrolitic methods

Thermal volatilization or pyrolysis of solid samples followed by gas chromatography–mass spectrometry (TV–GC–MS) or other downstream analyses has proven robustness and has been adopted for the extraction of organic compounds for their detection in planetary lander science missions (e.g., Viking Lander GC–MS, Phoenix TEGA, MSL SAM, and the future ExoMars MOMA). Pyrolysis to extract organic compounds from soil has limitations when oxidants co-occur in the analyzed sample unless the desired end product is CO2. Pyrolysis of such soils may result in oxidation of organics to CO2 during heating, and thus make organics characterization difficult, if not impossible. Analytical investigations seeking to identify organics in martian soils containing oxidants could benefit from the deployment of technologies that remove known and putative oxidants prior to thermal volatilization. We conducted a series of experiments in order to determine if a polymeric anion exchange resin, commonly used for removing the perchlorate anion from contaminated municipal water supplies, could sustain its substantial perchlorate removal capability while keeping organic compounds intact for downstream detection. We demonstrated that this resin can strongly bind perchlorate from aqueous solution while simultaneously leaving amino acids substantially unaltered. The perchlorate-binding resin could be easily adopted as a pre-treatment for martian soil extracts to create analytical systems with improved organics characterization capabilities compatible with existing TV–GC–MS systems. We propose this strategy to aid detection and characterization of putative martian organics co-situated with perchlorate at sampling sites.