Rapid identification of Pterocarpus santalinus and Dalbergia louvelii by FTIR and 2D correlation IR spectroscopy

Abstract Since Pterocarpus santalinus and Dalbergia louvelii , which are of precious Rosewood, are very similar in their appearance and anatomy characteristics, cheaper Hongmu D. louvelii is often illegally used to impersonate valuable P. santalinus , especially in Chinese furniture manufacture. In order to develop a rapid and effective method for easy confused wood furniture differentiation, we applied tri-step identification method, i.e., conventional infrared spectroscopy (FT-IR), second derivative infrared (SD-IR) spectroscopy and two-dimensional correlation infrared (2DCOS-IR) spectroscopy to investigate P. santalinus and D. louvelii furniture. According to FT-IR and SD-IR spectra, it has been found two unconditional stable difference at 848 cm −1 and 700 cm −1 and relative stable differences at 1735 cm −1 , 1623 cm −1 , 1614 cm −1 , 1602 cm −1 , 1509 cm −1 , 1456 cm −1 , 1200 cm −1 , 1158 cm −1 , 1055 cm −1 , 1034 cm −1 and 895 cm −1 between D. louvelii and P. santalinus IR spectra. The stable discrepancy indicates that the category of extractives is different between the two species. Besides, the relative stable differences imply that the content of holocellulose in P. santalinus is more than that of D. louvelii , whereas the quantity of extractives in D. louvelii is higher. Furthermore, evident differences have been observed in their 2DCOS-IR spectra of 1550–1415 cm −1 and 1325–1030 cm −1 . P. santalinus has two strong auto-peaks at 1459 cm −1 and 1467 cm −1 , three mid-strong auto-peaks at 1518 cm −1 , 1089 cm −1 and 1100 cm −1 and five weak auto-peaks at 1432 cm −1 , 1437 cm −1 , 1046 cm −1 , 1056 cm −1 and 1307 cm −1 while D. louvelii has four strong auto-peaks at 1465 cm −1 , 1523 cm −1 , 1084 cm −1 and 1100 cm −1 , four mid-strong auto-peaks at 1430 cm −1 , 1499 cm −1 , 1505 cm −1 and 1056 cm −1 and two auto-peaks at 1540 cm −1 and 1284 cm −1 . This study has proved that FT-IR integrated with 2DCOS-IR could be applicable for precious wood furniture authentication in a direct, rapid and holistic manner.