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Adsorption of pinosylvin onto different species of fresh and stored wood

Ildiko Mohammed-Ziegler, Allan Holmgren, Willis Forsling, Maine Ranheimer

The adsorption of pinosylvin- a natural antifungal agent - on wood was studied byRamanmicroprobe technique. The adsorption properties of twelve different European wood species were compared. The effect of solvents used, heat treatment, and prolonged storage of the samples on pinosylvin adsorption ability was analysed by means of the Raman intensity ratios of characteristic lines. Itwas found that the surface concentration of pinosylvin increased when the Lewis acidity of the solvent increased. Besides, adsorption of pinosylvin was less efficient on during prolonged storage the surface of wood became more hydrophobic after prolonged sample storage. In case of heat treatment (120ï‚°C, 3 h) no remarkable effect on the amount of adsorbed pinosylvin was observed. Simultaneously, the intensity of the fluorescence background increases. Moreover, the possible influence of B.E.T. specific surface area and lignin content (described by the kappavalue) on the amount of adsorbed pinosylvin was investigated.As revealed, B.E.T. specific surface area did not vary significantly between the different wood species, and therefore it has no significant effect on the efficiency of pinosylvin adsorption. However, the surface concentration of pinosylvin seems to increas with the lignin content. The amount of solvent residue in each sample wasmeasured by diffuse reflectance infrared Fourier transform (DRIFT) technique. For a few wood samples (e.g. pine heartwood, ash, and Hungarian oak) UV-Raman scattering was used to characterize the aromatic components of these wood species. The morphology of the samples was investigated with the aid of scanning electron microscopy (SEM) images. Furthermore, the B.E.T. specific surface area was found not to vary significantly between the different wood species, and therefore it has no significant effect on the efficiency of pinosylvin adsorption. However, the surface concentration of pinosylvin seems to increas with the lignin content. DRIFT spectroscopy was found to be useful to detect solvent residue in the wood samples and the evaporation of polar solvents is a rather slow process. However, it was not possible to detect adsorbed pinosylvin by DRIFT measurements, due to the low concentration and the lack of characteristic frequencies differing from other wood constituents.