In-Situ Organic Extraction, Separation and Detection using Supercritical CO2 and Superheated Water

Scientific Objectives: New in situ instruments and strategies are being developed to determine the abundance and distribution of biogenic elements and organic compounds in space and to determine whether indigenous organisms exist (or existed) anywhere on these bodies. While development and maturation of analysis technologies has flourished, front-end sample handling and preparation systems are still underdeveloped. These technologies are crucial for the future of planetary exploration. We aim to address this need by building a breadboard extraction and separation instrument to extract and separate astrobiologically-important organic compounds that uses only supercritical CO2 (scCO2, 40-75 °C) and superheated water (SHW, up to 200 °C). In our previous ASTID and COLDTECH-funded work, we have demonstrated that scCO2 can extract and separate ppb and ppt-level nonpolar and slightly polar species from complex salty samples at 40-75 °C [1,2]. For polar species, water is a good solvent, but water can also dissolve salt, which can cause issues for detection instruments. No methodology has yet been developed to eliminate salt while retaining a wide variety of polar compounds. Our proposed integrated instrument will solve this problem by using preconcentration traps and chromatography columns to separate and deliver salt-free analytes to a mass spectrometer. No pyrolysis or harsh organic solvents will be used. Our proposed approach will enable the extraction and analysis of biomarkers of a full range of polarities. Approach: The instrument will be operated in two steps for each solvent. 1) Unaltered biomarkers will be extracted (along with salts for SHW, if present) from solid or liquid or mixed samples. The extraction solution will flow through the on-line solid-phase trap column which will trap and preconcentrate the compounds of interest at ambient temperature while rejecting any salt species [3]. 2) Either scCO2 or SHW with a temperature ramp (50-200 °C) will be used to release the preconcentrated compounds from the trap column. The eluted molecules will then be carried into the separation (chromatography) column, where the compounds will be separated using only scCO2 or SHW before being introduced into a detector, in this case an electrospray ionization mass spectrometer. This proposed work will include the selection and testing of off-the-shelf stationary phases, full method development for SHW (including temperature programming and flow optimization), and validation with a variety of sample types and analytes. We will provide quantitative measurements of this instrument's extraction efficiency and detection limits to ensure efficient detection of important biomarkers and that salts do not interfere with the analysis. Relevance to the PICASSO Program: The proposed instrument meets the key science requirement to detect and identify low-abundance organic molecules and astrobiologically-relevant species in future planetary missions, for terrestrial-like planets such as Mars, small bodies (comets, asteroids), or icy satellites (Europa, Enceladus, etc.). Our approach, which enables broad mass spectrometric detection of organics without derivatization, is robust and insensitive to salt content. Prior efforts to develop pressurized water extraction (e.g. the Urey instrument developed for Mars) have relied on higher-risk methods with extraction temperatures >200 °C and requiring fluorescent molecular tags to identify specific classes of analytes [4]. Our proposed instrument minimizes risk: it is not analyte-specific, requires no organic solvents or reagents or molecular tags, and uses only the minimum needed temperatures for analysis, thus ensuring preservation and identification of species in their native forms. 1 McCaig, et al. Astrobiol, 2016. 16: 703 2 Menlyadiev, et al. Int J Astrobiol, 2018. 1-10 3 Andrade-Eiroa, A. et al. Trends Anal Chem, 2016. 80: 641-654 4 Amashukeli, et al. Astrobiol, 2008. 8: 597