Elucidation of aquatic humic partial structures by multistage ultrafiltration and two-dimensional nuclear magnetic resonance spectrometry

Two-dimensional heteronuclear multiple quantum coherence (HMQC) H-1-NMR was successfully applied to structural investigations of aquatic humic substan ce (HS) fractions obtained from multistage ultrafiltration (MST-UF) of a se lected bog water HS (HO13-XAD8, German Research Program DFG-ROSIG). Details of the HMQC H-1-NMR novel in HS characterization are presented. The result s of the combined procedure point out that structural units in isolated HS can be enriched in different mass fractions, for instance fatty acids in th e fraction <1kDa, amino acids in the 10-50 kDa fraction and methyl groups a ttached to quaternary carbon atoms in the high molecular mass fraction >50 kDa.