Structural elucidation of isolated and fractionated lignins by means of ultra-high resolving mass spectrometry (LignoMassStructure)

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The goal of this research project is a development of ESI- and GALDI-FT-ICR-MS and tandem MS routines for a characterization of isolated and fractionated lignins from different plants (coniferous wood, deciduous wood and annual plants) and pulping processes (kraft, sulfite and soda pulping). These routines will massively help to reduce the effort for an analysis of soluble and insoluble lignin samples, in comparison to classical analytical methods for a lignin characterization (e.g., GPC, NMR, Py-GC/MS). On the one hand, general sample information are accessible with these FT-ICR-MS and -MS/MS methods, such as molar mass distribution. On the other hand, also specific structural insights into the lignin samples are obtainable by these experiments. For this purpose, method development and optimization experiments will be performed with the help of a fractionated kraft lignin from deciduous wood (beech). In addition, a hetero spectroscopic correlation approach will be applied to combine the FT-ICR-MS and -MS/MS results with results from other analytical techniques (Py-GC/MS, 13C-, 31P- and 2D-HSQC-NMR spectroscopy), which will help to obtain more information about the structural composition of the different lignins. These novel results will significantly increase our understanding of the influence of an isolation process on the lignin target structure. Especially the GALDI-FT-ICR-MS and -MS/MS analyses of solid lignin samples will be helpful to characterize the lignin structure more detailed, independently from the solubility of the lignin compounds contained in the different samples or sample fractions. In the last project phase, the capabilities of the developed methods will be demonstrated by analyzing a complex lignocellulose, which will help to evaluate the applicability of the developed routines for other biopolymers (cellulose and hemicellulose). If this method application step is successful, for the first time ever, a structural characterization of biopolymers in their native environment is possible. Therefore, the results from this research project will have an impact on the development of more effective and expedient isolation and modification procedures for biopolymers, which will significantly contribute to a production of lignin and lignocellulose based products of higher value in the near future.