Immunological detection of mellitic acid in the Atacama desert: Implication for organics detection on Mars

abstract The restrictions imposed by instrumentation and some methodological constraints make that only vola-tile organic compounds have been analyzed by in situ instruments in planetary exploration. It has beenargued that polycarboxilic acids like the hexacarboxylic acid (mellitic acid) can be produced and accumu-lated in the martian regolith from the oxidation of meteoritic organic matter. However, these compoundsare non-volatile and instruments designed for the analysis of volatile compounds would not detect them.Herein we report the production of an antibody to mellitic acid and the development of a fluorescentinhibition microarray immunoassay (IMI) to detect this substance to a limit of 5 ppb (ng mL 1 ). We usedthe anti-mellitic antibody to detect mellitic acid in drill core samples obtained from different depths inthe Atacama desert (Chile), a highly relevant terrestrial analogue for Mars. The presence of mellitic acidwas corroborated by organic extraction and GC/MS analysis. Our results showed a smooth gradient ofmellitic acid concentration, being higher at the surface and near the surface (1.17–1.57 ppm) and dimin-ishing with depth to be undetectable at a depth of 4 m. Our immunoassay can be easily implemented ininstruments for in situ analysis. 2012 Elsevier Inc. All rights reserved.

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