Fast screening for hydrolysable and condensed tannins in lignocellulosic biomass using reactive Py-GC/MS with in situ silylation

Rapid screening techniques for lignocellulosic biomass are required for the development of efficient conversion strategies in the field of biofuels and value-added chemicals. This is particularly true for tannins, which are highly valuable in the tannery and nutraceutical industries. In the present work, we propose a quick method based on reactive pyrolysis with in situ hexamethyldisilazane (HMDS) derivatization followed by GC/MS analysis for the qualitative determination of tannins in lignocellulosic biomass. Different pyrolysis times were used to study pyrolysis mechanisms of tannins. Reference compounds belonging to hydrolysable and condensed tannins, both in monomeric and polymeric forms, were used to select specific pyrolysis products that could be used as markers. When pyrolysis time was increased, hydrolysable tannins were found to be highly thermostable, while condensed tannins showed extensive degradation. An optimal pyrolysis time was determined to reduce the number of peaks and increase the abundances of the most characteristic components. The results were applied to assess the presence of tannins in four different biomass: oak gall nuts, hazelnut cuticles, grape seeds and pomegranate bark.