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

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 (DF_T), lignin bands only (DF_L) and polysaccharides bands only (DF_P), to explore the ability of FTIR-ATR to separate between species and growing location. The DF_L model enabled a good separation between pine species, whereas the DF_P model enabled differentiation for both species and growing location. The DF_T 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.