Molecular compounds generated by ruthenium tetroxide oxidation and preparative off line thermochemolysis of lignite humic acids from South Moravia: Implications for molecular structure

The composition of humic acids (HAs) isolated from a South Moravian lignite deposit was examined via thermochemolysis and RuO 4 oxidation. The combination of thermochemolysis with TMAH and TEAAc shows that fatty acids were mostly in a “free” form, tightly trapped within the humic acid organic network. Humic acids contain also trapped hydrocarbons. The relative distributions of these compounds confirm their higher plant origin. RuO 4 oxidation resulted in a lipophilic fraction containing mainly fatty acids. The hydrophilic fractions released upon RuO 4 oxidation comprised mostly aliphatic C 2–C 9 dicarboxylic acids and hydroxy acids related to short methylene bridges, to bridges between aromatic and/or oxygenated moieties such as aliphatic chains of ligneous units.