10:45 AM - 11:00 AM
[PPS06-07] In-situ analysis of organic compounds in the Murchison meteorite using desorption electrospray ionization coupled with an Orbitrap mass spectrometer.
★Invited Papers
Keywords:Organic compounds in primitive meteorites, Desorption electrospray ionization, High mass resolution imaging
[INTRODUCTION] Primitive meteorites contain a wide variety of organic species. Recent studies using high-resolution mass spectrometry equipped with liquid chromatography revealed presence of various CHO, CHNO, CHNOS [1] and CHN species in solvent extracts from Murchison meteorite [2, 3]. The organic compounds would be synthesized and evolved through oxidation and reduction processes during aqueous alteration on the parent body [3]. To understand the chemical evolution of the organic compounds in primitive meteorites, investigation of their spatial distribution and relationship with minerals is very important.
Two-dimensional (2D) analysis using desorption electrospray ionization (DESI) coupled with mass spectrometry can achieve non-destructive and ambient in-situ analysis to reveal the spatial distribution of organic molecules [6, 7]. This technique is effective for analysis of polar organic species (e.g. CHN and CHNO compounds) compared to laser based ionization technique. In this study, we performed the 2D DESI-MS imaging using high-resolution mass spectrometry (HRMS) on surface of Murchison meteorite.
[EXPERIMENTAL] The fragments with flat surface (~ a few mm) of Murchison meteorite were obtained by chipping and were pressed in Indium. The 2D DESI-HRMS imaging was performed on surface using a DESI ion source (Omni Spray Source 2D, Prosolia) equipped with a hybrid quadrupole-Orbitrap mass spectrometer (Q-Exactive Plus, Thermo Scientific). Methanol (LCMS grade) was sprayed on the sample surface with 1–2µl/min of flow rate. The DESI-HRMS (~140,000@m/z 200) imaging was performed in a clean room (class 1000) at the Research Center for Planetary Trace Organic Compounds of Kyushu University, After the imaging, the sample was subsequently observed using FE-SEM (JEOL JSM-7001F) equipped with an EDS (Oxford INCA Energy). The FE-SEM observation was carried out with no coating on the sample.
[RESULTS AND DISCUSSION] Numerous ion peaks with m/z 70-700 were detected from sample surface. Among the peaks, alkylated homologues of CnH2n-1N2+ (n=9–14) and CnH2nNO+ (n=6–9) were detected in the Murchison meteorite distinguishing from surrounding metal. Both compounds could be assigned within < 3 ppm in mass precision. Our previous study using HPLC/HPMS analyses revealed that alkylated homologues of imidazole (CnH2n-1N2+) were dominant in the MeOH extract of the Murchison meteorite [2, 3]. Although the detailed structures of these compounds could not be defined in this experiment, the CnH2n-1N2+ compounds detected through DESI-HRMS imaging could correspond to the alkylimidazole homologues. Our results suggest usefulness of the DESI-MS analysis for understanding of spatial distribution of polar organic species in primitive meteorites. The CnH2n-2N2 compounds were mainly distributed in matrix region of Murchison. Homologues of CnH2nNO+ except C6H12NO+ showed roughly homogeneous distribution in the matrix region. On the other hand, distribution of C6H12NO+ was clearly different from other homologues and it was concentrated in the edge of the fragment. The compound distribution could have a relationship to secondary altered minerals (phosphates associated with clay minerals, which may be PCP) in Murchison. The observation would indicate that C6H12NO+ experienced different chemical evolution from other homologues of CnH2nNO+, and possible processes would be oxidation and/or chromatographic effect during hydrothermal processes on the parent body of Murchison. Further analysis will be performed to determine the mineral phases in the fragment in near future.
[REFERENCES] [1] Schmitt-Kopplin P. et al. 2010. PNAS, 107:2763. [2] Yamashita Y. and Naraoka H. 2014. Geochem. J, 48: 519. [3] Naraoka H. et al. 2017. ACS, 540-550. [4] Clemett S. J. et al. 1993. Science, 262:721. [5] Ito M. et al. 2016, Goldschmidt Conference, 2016. #1297. [6] Takáts. Z. et al. 2004. Science, 306: 471. [7] Naraoka H. and Hashiguchi M. 2016, 79th Ann. Meeting, Met. Soc. #6169.
Two-dimensional (2D) analysis using desorption electrospray ionization (DESI) coupled with mass spectrometry can achieve non-destructive and ambient in-situ analysis to reveal the spatial distribution of organic molecules [6, 7]. This technique is effective for analysis of polar organic species (e.g. CHN and CHNO compounds) compared to laser based ionization technique. In this study, we performed the 2D DESI-MS imaging using high-resolution mass spectrometry (HRMS) on surface of Murchison meteorite.
[EXPERIMENTAL] The fragments with flat surface (~ a few mm) of Murchison meteorite were obtained by chipping and were pressed in Indium. The 2D DESI-HRMS imaging was performed on surface using a DESI ion source (Omni Spray Source 2D, Prosolia) equipped with a hybrid quadrupole-Orbitrap mass spectrometer (Q-Exactive Plus, Thermo Scientific). Methanol (LCMS grade) was sprayed on the sample surface with 1–2µl/min of flow rate. The DESI-HRMS (~140,000@m/z 200) imaging was performed in a clean room (class 1000) at the Research Center for Planetary Trace Organic Compounds of Kyushu University, After the imaging, the sample was subsequently observed using FE-SEM (JEOL JSM-7001F) equipped with an EDS (Oxford INCA Energy). The FE-SEM observation was carried out with no coating on the sample.
[RESULTS AND DISCUSSION] Numerous ion peaks with m/z 70-700 were detected from sample surface. Among the peaks, alkylated homologues of CnH2n-1N2+ (n=9–14) and CnH2nNO+ (n=6–9) were detected in the Murchison meteorite distinguishing from surrounding metal. Both compounds could be assigned within < 3 ppm in mass precision. Our previous study using HPLC/HPMS analyses revealed that alkylated homologues of imidazole (CnH2n-1N2+) were dominant in the MeOH extract of the Murchison meteorite [2, 3]. Although the detailed structures of these compounds could not be defined in this experiment, the CnH2n-1N2+ compounds detected through DESI-HRMS imaging could correspond to the alkylimidazole homologues. Our results suggest usefulness of the DESI-MS analysis for understanding of spatial distribution of polar organic species in primitive meteorites. The CnH2n-2N2 compounds were mainly distributed in matrix region of Murchison. Homologues of CnH2nNO+ except C6H12NO+ showed roughly homogeneous distribution in the matrix region. On the other hand, distribution of C6H12NO+ was clearly different from other homologues and it was concentrated in the edge of the fragment. The compound distribution could have a relationship to secondary altered minerals (phosphates associated with clay minerals, which may be PCP) in Murchison. The observation would indicate that C6H12NO+ experienced different chemical evolution from other homologues of CnH2nNO+, and possible processes would be oxidation and/or chromatographic effect during hydrothermal processes on the parent body of Murchison. Further analysis will be performed to determine the mineral phases in the fragment in near future.
[REFERENCES] [1] Schmitt-Kopplin P. et al. 2010. PNAS, 107:2763. [2] Yamashita Y. and Naraoka H. 2014. Geochem. J, 48: 519. [3] Naraoka H. et al. 2017. ACS, 540-550. [4] Clemett S. J. et al. 1993. Science, 262:721. [5] Ito M. et al. 2016, Goldschmidt Conference, 2016. #1297. [6] Takáts. Z. et al. 2004. Science, 306: 471. [7] Naraoka H. and Hashiguchi M. 2016, 79th Ann. Meeting, Met. Soc. #6169.