LUCIA - Ion Chromatograpy for ultra-trace analysis in aqueous planetary envionments: A key instrument for Martian and Lunar bases and icy Moon exploration

The identification of soluble inorganic and organic species is central to understanding
geochemical processes, assessing habitability, and searching for biosignatures across planetary
environments. On Mars, the detection of salts such as chlorides, sulfates, nitrates, and
particularly perchlorates has revealed complex aqueous histories, while simultaneously
highlighting a major analytical limitation: the oxidative nature of perchlorates interferes the
detection of organics with thermal techniques such as GC-MS, due to the degradation of organic
compounds and potential false negatives. ^{1, 2}
In this context, ion chromatography (IC) has emerged as a robust alternative capable of
overcoming these challenges when searching for soluble inorganic and organic compounds.
Building on the analytical methodology presented in previous work (Prieto-Taboada et al., 2025),
we report here its further development and validation within the framework of LUCIA
(Ultra-Compact Ion Chromatography Laboratory for in situ Analysis), an instrument currently
under maturation by a European consortium with strong expertise in space instrumentation and
analytical chemistry. ³
While initially motivated by Martian exploration, the applicability of this approach extends
naturally to any environment where water (soils, brines, etc.) or ice is present. In particular, icy
moons such as Enceladus (both plumes and surface ice), Titan (solid samples in evaporitic ground
terrains), as well as future Mars and Lunar exploration scenarios (water ice deposits and fine-
grained regolith), represent highly relevant targets. In these contexts, water is both the
extraction medium and the primary matrix of interest, making IC especially suitable for direct
chemical analysis of soluble compounds. For the Moon, this capability is directly linked to future
in-situ resource utilization and water quality assessment for sustained human presence,
whereas for icy bodies, it enables the study of dissolved species in ice or plume directly related to
habitability and prebiotic chemistry. ^{1, 2, 4}
The developed method enables the simultaneous determination of a wide range of inorganic
anions and low-molecular-weight organic acids in a single analysis. These organic species,
including short-chain carboxylic acids, are of particular interest as potential biosignatures or
indicators of prebiotic processes. This combined analytical capability represents a clear
advantage over ion-selective electrodes, which are intrinsically limited to single analytes, and
complements GC-MS by providing reliable chemical information even in oxidizing matrices.
A key aspect of the method development was the separation of short-chain organic acids at
ultra-trace levels. This required the implementation of a gradient elution program beginning at
extremely low eluent strength (Na2CO3 0,25 mM), ensuring sufficient resolution (Rs > 1,1)
between structurally similar compounds at concentrations down to the ppb (micrograms/kilo) range. As the gradient progresses, the increasing eluent strength enables the elution of more
strongly retained species without compromising early-stage separation.
Method validation confirms robust quantitative performance over a concentration range from
10 ppb to 5 ppm. Two calibration ranges are required to cover this interval, both showing
excellent analytical quality (R2 > 0,99, relative standard deviation below 3%, relative error under
5%, and limit of detections between 1 ppb and 4,5 ppb).
During the validation process, a slight variation in retention times was observed at different
concentration levels under low eluent-strength conditions. This effect is currently under
investigation and may be associated with equilibria that become significant only at very low
eluent strengths, unlike under conventional operating conditions. Nevertheless, this does not
compromise the analytical performance of the method, and both qualitative and quantitative
analyses can be performed reliably.
The integration of this methodology within the LUCIA instrument further reinforces its relevance
for space applications. The system provides multicomponent analysis in a single run, is not
affected by perchlorate interference, and significantly enhances the interpretation of
complementary techniques such as GC-MS. Compared to traditional approaches, it enables a
more comprehensive chemical characterization with fewer measurements and higher
information yield.
Overall, these results demonstrate that ion chromatography is not only suitable but highly
advantageous for ultra-trace analysis of soluble compounds in aqueous planetary environments.
Its implementation in future missions to Mars, the Moon, or icy moons such as Enceladus and
Titan would provide critical insights into geochemistry, water quality, and potential
biosignatures, supporting both robotic exploration and future human activities.
Acknowledgements
This work has been supported through the PAMMAT project “Alteration processes in Mars and
Moon Meteorites, and Terrestrial Analogues at different environments: Mars2020, Rosalind
Franklin and Returned Samples from Mars and Moon” (Grant No. PID2022-142750OB-I00),
funded by the Spanish Agency for Research (MICIU/AEI/10.13039/501100011033/FEDER/UE).

Keywords: Ion Chromatography, LUCIA Instrument, Ultratrace Analysis, Organic Acids, Inorganic
Anions, Planetary Exploration.
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