In situ organic compound analysis on a meteorite surface by desorption electrospray ionization coupled with an Orbitrap mass spectrometer

Rationale: Since extraterrestrial organic matter in meteorites is a very complex mixture that is hard to ionize due to its association with minerals, in situ analysis of polar organic compounds has never been performed. In addition, when studying powdered samples, spatial information of organic compounds is lost. Methods: In situ molecular analysis and chemical imaging of polar organic compounds were performed on a meteorite surface by desorption electrospray ionization coupled with high-resolution mass spectrometry (DESI-HRMS) using an Orbitrap mass spectrometer. Results: Many CHN compounds, including alkylated pyridine and imidazole homologues, were identified from the complex peaks by HRMS using a spray of electrically charged methanol with a spatial resolution of approximately 50 μm. The same alkylated homologues have the same spatial distribution in the meteorite matrix, while alkylpyridines occur in a different location from alkylimidazoles. Conclusions: The compound distribution suggests a different source for each compound series or a chromatographic separation effect associated with fluid movement in the meteorite parent body. The DESI-HRMS imaging will further our understanding of organic compound distribution with respect to mineral and water interactions in meteorites.