Identification of three Diospysros species using FT-IR and 2DCOS-IR

Abstract

Based on the systematic analysis of heartwood and alcohol extractives of D. ebenum, D. philippinensis and D. celebica by the three-step infrared spectroscopy (FT-IR, SD-IR and 2DCOS-IR), the three similar Diospyros wood are successful distinguished. In FT-IR spectra, the principal chemical components of heartwood are characterized for cellulose (the bands at around ∼1370, ∼1158, ∼1034 and ∼895 cm−1), lignin (the bands around ∼2935, ∼1510, ∼1462 and ∼1426 cm−1) and calcium oxalate (peaks at ∼1615, ∼1318 and ∼781 cm−1). The correlation coefficient among samples and standard material give the result that D. ebenum is lignin-rich and D. celebica is resin-rich, while D. philippinensis contains more calcium oxalate. In SD-IR spectra, D. philippinensis and D. celebica have peaks at 1731 cm−1 mean they contain more resin. Besides, the alcohol extracts of D. ebenum possesses stronger peak at 1651, 1632, 1584 and 1388 cm−1 which can be characterized for naphthalene derivatives component. Through the 2DCOS-IR synchronous spectra, the C–H of lignin (the auto peaks at ∼1450 and ∼1460 cm−1) of three heartwoods show strong intensity. Lignin shows high thermal sensitivity in D. ebenum, while it is similar sensitive with cellulose in D. philippinensis, but it is slightly lower thermal perturbation than cellulose in D. celebica.Meanwhile, the thermal sensitivity of Si–O and Si–C of alcohol extractives are different in the range of 935–1255 cm−1. In addition, the difference in thermal perturbation of CO and CN of resin and naphthalene derivatives could also be considered as the key factors to discriminate them. This research demonstrated that the FT-IR and 2DCOS-IR could analyze and discriminate confused ebony wood comprehensively.