Distinction of four Dalbergia species by FTIR, 2nd derivative IR, and 2D-IR spectroscopy of their ethanol-benzene extractives

Four common species of Dalbergia genus (D. bariensis, D. oliveri, D. cochinchinensis, and D. retusa), which are traded as "Rosewood" or "Hongmu" commonly throughout East and Southeast Asia, were extracted with ethanol-benzene and the extractives were analyzed by means of three IR spectroscopic methods aiming at their chemotaxonomic differentiation. Conventional FTIR and 2nd derivative IR (SD-IR) showed defined spectral ranges, where the differences are pronounced. Two-dimensional correlation infrared (2D-IR) spectroscopy revealed significant auto-peaks suitable for reliable differentiation of the four Dalbergia species. The gas chromatography-mass spectrometry (GC-MS) evaluation of the extractives was also useful. It can be concluded that the analysis of the extractives is the best chemotaxonomic approach for identification of anatomically similar wood species.