Differentiation between pine woods according to species and growing location using FTIR-ATR

Abstract

Attenuated total reflectance-Fourier transform infrared (FTIR-ATR) spectroscopy was applied to 120 samples of heartwood rings from eight individual pine trees from different locations in Spain. Pinus sylvestris cores were collected at the Artikutza natural park (Ps-ART). Pinus nigra cores were collected in Sierra de Cazorla (Pn-LIN) and in La Sagra Mountain (Pn-LSA). Three discriminant analysis tests were performed using all bands (DFT), lignin bands only (DFL) and polysaccharides bands only (DFP), to explore the ability of FTIR-ATR to separate between species and growing location. The DFL model enabled a good separation between pine species, whereas the DFP model enabled differentiation for both species and growing location. The DFT model enabled virtually perfect separation, based on two functions involving twelve FTIR bands. Discrimination between species was related to bands at 860 and 1655 cm−1, which were more intense in P. sylvestris samples, and bands at 1425 and 1635 cm−1, more intense in P. nigra samples. These vibrations were related to differences in lignin structure and polysaccharide linear chains. Discrimination between growing locations was mainly related to polysaccharide absorptions: at 900, 1085 and 1335 cm−1 more representative of Pn-LIN samples, and at 1105 and 1315 cm−1 mostly associated to Pn-LSA samples. These absorptions are related to β-glycosidic linkages (900 cm−1), cellulose and hemicellulose (C–O bonds, 1085 and 1105 cm−1) and content in amorphous/crystalline cellulose (1315 and 1335 cm−1). These results show that FTIR-ATR in combination with multivariate statistics can be a useful tool for species identification and provenancing for pine wood samples of unknown origin