Automated Aqueous Sample Concentration Methods for in situ Astrobiological Instrumentation

The era of wet chemical experiments for in situ planetary science investigations is upon us, as evidenced by recent results from the surface of Mars by Phoenix’s microscopy, electrochemistry, and conductivity analyzer, MECA [1]. Studies suggest that traditional thermal volatilization methods for planetary science in situ investigations induce organic degradation during sample processing [2], an effect that is enhanced in the presence of oxidants [3]. Recent developments have trended towards adaptation of non-destructive aqueous extraction and analytical methods for future astrobiological instrumentation. Wet chemical extraction techniques under investigation include subcritical water extraction, SCWE [4], aqueous microwave assisted extraction, MAE, and organic solvent extraction [5]. Similarly, development of miniaturized analytical space flight instruments that require aqueous extracts include microfluidic capillary electrophoresis chips, μCE [6], liquid-chromatography mass-spectrometrometers, LC-MS [7], and life marker chips, LMC [8]. If organics are present on the surface of Mars, they are expected to be present at extremely low concentrations (parts-per-billion), orders of magnitude below the sensitivities of most flight instrument technologies. Therefore, it becomes necessary to develop and integrate concentration mechanisms for in situ sample processing before delivery to analytical flight instrumentation. We present preliminary results of automated solid-phase-extraction (SPE) sample purification and concentration methods for the treatment of highly saline aqueous soil extracts. These methods take advantage of the affinity of low molecular weight organic compounds with natural and synthetic scavenger materials. These interactions allow for the separation of target organic analytes from unfavorable background species (i.e. salts) during inline treatment, and a clever method for selective desorption is utilized to obtain concentrated solutions on the order of 100μL from 1-10 mL of aqueous sample extract. The selective desorption process involves the derivatization of target analytes in the liquid state which acts to sequester these compounds by reducing their affinity towards the scavenger material. These processes show potential for a single step protocol for the purification of aqueous soil extracts and offer concentration factors of 10-100. These inline processing methods will help address problems of insufficient detection limits for organic detection on Mars and allow for integration as a module within future aqueous in situ flight instruments. REFERENCES: [1] Hecht, M., et al., Science 325, 64-67, 2009. [2] Navarro-González, R., et al., Geophys. Res. Abs., 11, 1549, 2009. [3] Ming, D.W., et al., 40th LPSC Conference, #2241, 2009. [4] Amashukeli, X., et al., J. Geophys. Res., 112, G04S16, 2007. [5] Buch, A., et al., J. Chromatogr. A, 999, 165, 2003. [6] Skelley, A.M., et al., Proc. Natl. Acad. Sci. U.S.A., 104, 1041-1046, 2005. [7] Liu, D.-L., L.W. Beegle, L.W. and I. Kanik, Astrobiology, 8, 229-241, 2008. [8] Sims, M., et al., AbSciCon, #2-16-P, 2008.