Isotopic exchange mass spectrometry reveals molecular structure of Natural Organic Matter

摘要

We identified number of labile hydrogens in 450 species and number both of labile hydrogens and oxygens in 231 species in the NOM from Suwannee River. Compact visual representation of the obtained data was performed using 2D and 3D Van Krevelin diagram and Kendrick mass defect diagram which can be useful for classification of different NOM samples. The observed number of labile hydrogens in NOM molecules varies from 2 to 7 and increases with molecular weight. Also we observed that there are non-labile oxygens atoms in NOM molecules. Those atoms stems from ether group. The number of non labile oxygens atoms increases with molecular weight. We demonstrated that both information about labile hydrogens and labile oxygens can be useful together for the structural characterization of particular molecules in mixture. For example our results showed that molecule C14H18O8 (DBE=6) has 4 labile hydrogens and 1 non-labile oxygen. Thus we can conclude that four -OH groups and 3 labile oxygens attached to carbon with double bound are presented in the molecule. Considering possible structures (C14H18O8) and information above we found that the molecule structure is mostly close to flavon unit.