Assessment of historic Tilia codrata wood by solid-state C CPMAS NMR spectroscopy

Historic lime (Tilia cordata Mill.) wood samples, differing by their provenance, conservation status and period have been investigated by solid-state carbon-13 cross polarization magic angle sample spinning nuclear magnetic resonance (¹³C CPMAS NMR) spectroscopy. Structural and chemical modifications were assessed by comparing the historic samples with a reference wood sample. The conventional NMR measurements followed by the ¹³C resonance integral intensities of the wood samples have been carried out in order to acquire information of the chemical changes due to the natural ageing process taking place over the years. The main results concern the decrease of the carbohydrates moiety, especially the decrease of the hemicelluloses and amorphous cellulose signals, while the signals for aliphatic and methoxyl carbons from lignin present and increase of the intensity up to 120 years then start to decrease. At the same time a slight widening of the amorphous carbohydrate signals was observed, which may evidence the occurring of some chemical rearrangements, with the formation of new chemical species. These lead in the ¹³C NMR spectra to the line broadening of the signals induced by their chemical shifts dispersion.