title: Isotope-Filtered 4D NMR Spectroscopy for Structure Determination of Humic Substances.
abstract: Humic substances, the main component of soil organic matter, could form an integral part of green and sustainable solutions to the soil fertility problem. However, their global-scale application is hindered from both scientific and regulatory perspectives by the lack of understanding of the molecular make-up of these chromatographically inseparable mixtures containing thousands of molecules. Here we show how multidimensional NMR spectroscopy of isotopically tagged molecules enables structure characterization of humic compounds. We illustrate this approach by identifying major substitution patterns of phenolic aromatic moieties of a peat soil fulvic acid, an operational fraction of humic substances. Our methodology represents a paradigm shift in the use of NMR active tags in structure determination of small molecules in complex mixtures. Unlike previous tagging methodologies that focused on the signals of the tags, we utilize tags to directly probe the identity of the molecules they are attached to.
authors.affiliation: EastChem School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Rd, Edinburgh EH9 3FJ (UK).
authors.forename: Nicholle G A
authors.initials: NG
authors.lastname: Bell
authors.affiliation: EastChem School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Rd, Edinburgh EH9 3FJ (UK).
authors.forename: Adam A L
authors.initials: AA
authors.lastname: Michalchuk
authors.affiliation: EastChem School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Rd, Edinburgh EH9 3FJ (UK).
authors.forename: John W T
authors.initials: JW
authors.lastname: Blackburn
authors.affiliation: School of Geosciences, University of Edinburgh, Grant Institute, James Hutton Road, Edinburgh EH9 3FE (UK).
authors.forename: Margaret C
authors.initials: MC
authors.lastname: Graham
authors.affiliation: EastChem School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Rd, Edinburgh EH9 3FJ (UK). dusan.uhrin@ed.ac.uk.
authors.forename: Dušan
authors.initials: D
authors.lastname: Uhrín
keywords: NMR spectroscopy; complex mixtures; humic substances; isotopic labeling