NMR-Spectroscopy - Renewable Resources

The Nuclear Magnetic Resonance (NMR) Spectroscopy group is engaged on the one hand in the structural elucidation of organic molecules and on the other hand in the analysis and characterization of complex mixtures on the molecular and supramolecular level. Applying and developing NMR-spectroscopic methods for components of lignocellulosic materials (celluloses, lignins, hemicelluloses, extracts), the group provides a central analytical tool to support other research groups of our institute. NMR spectroscopy can be performed both in solution (liquid NMR) and on gel-like or solid samples (solid-state NMR). The necessary equipment (e.g. probe heads) is available directly at our institute.

Liquid NMR is operated on a 400 MHz instrument equipped with a dual, N2-cooled broadband probe head with z-gradients or a cryo-probehead, which allows the analysis of small sample amounts (<0.5 mg). With the help of one- and multi-dimensional homo- and heteronuclear experiments, structure elucidation, conformation analysis or purity testing of synthesis products or isolated plant metabolites are performed. In addition, the analysis of complex mixtures, such as natural or technical lignins, celluloses and polysaccharides and their degradation products or biorefinery fractions, is carried out. Depending on the problem, measurements of hetero-nuclei other than 13C (19F, 29Si, 31P, 15N, 11B and others), quantitative measurements of different functional groups, measurements at variable temperatures or diffusion experiments (DOSY) are also used.

On the one hand, many material properties are simply lost in solution. On the other hand, some compounds, especially biopolymers, are completely insoluble in common solvents. For the characterization of such materials another 400 MHz spectrometer for solid-state NMR measurements is available. Gel-like samples, such as hydrogels, aerogels, many polysaccharides or lignin derivatives, can be analyzed with our HR-MAS (high-resolution magic angle spinning) probehead, while for solid and crystalline organic compounds (e.g., celluloses, organic-inorganic hybrid materials) our CP-MAS (cross polarization magic angle spinning) probehead is used.