Typically, extensive sample preparation procedures are required to perform analysis of natural organic matter (NOM) and soil organic matter. In this study, the solid NOM and unprocessed soil samples were fixed on a metal plate with double adhesive tape and the samples were directly analyzed by use of laser desorption ionization (LDI) coupled to ultrahigh resolution mass spectrometry (UHR-MS). LDI UHR-MS analysis was successfully performed with about 2–5 μg of solid fluvic and humic acid and 500 μg soil samples loaded on the metal plate. Most of the peaks reported in the previous study performed with LDI UHR-MS was observed and additional 2200 peaks were found by direct analysis of fluvic acids. Two unprocessed soil samples were directly analyzed with LDI UHR-MS. Poly-condensed aromatics, oxygenated poly-condensed aromatics, Lignin type molecules, and lipid molecules were mainly observed from two soil samples were most abundantly observed from soils. The data presented in this study clearly show that direct molecular level analysis can be performed on solid NOM and unprocessed soil samples with high sensitivity. Therefore, we expect that the suggested analytical method can be very useful for studies such as obtaining profiles of organic compounds in cored soil samples.
Keywords: natural organic matter, soil, laser, desorption