Impact Analysis of Infrared Spectra in Pterocarpus santalinus and Confused Species Coated with Wood Wax Oil
LIU Jing1, HUANG An-min2, ZHANG Qiu-hui1*
1. College of Materials Science and Technology，Beijing Forestry University，Beijing 100083，China
2. Research Institute of Wood Industry，Chinese Academy of Forestry，Beijing 100091，China
Abstract：The wood characteristics of P. tinctoricus Welw and Dalbergia louuelii are similar to Pterocarpus santalinu. Especially，after the two species have been painted with colored wood wax oil, it is difficult to distinguish from P. tinctoricus Welw, Dalbergia louuelii and Pterocarpus santalinu. As many rosewood furniture sold on the market are mostly surface-finished in order to achieve anti-corrosion, dust-proof, anti-cracking properties, as well as to improve the surface gloss and the texture of precious wood, the identification of wood itself is far from meeting market demand. Pterocarpus santalinus, P. tinctoricus Welw and Dalbergia louuelii finished with Wood wax oil were analyzed by the Tri-step Infrared identification（FTIR, SDIR and 2D-IR）. The three species were surface finished by Polishing-Carrier oil-Polishing-Coating oil-Drying. The wood powder of three species themselves and three surface-coated samples were analyzed by means of three IR spectroscopic methods, and the FTIR spectrum of wood wax oil was also determined. The results show that: (1) The FTIR spectrum of wood wax oil has strong peak at 2 925, 1 733, 1 465 and 1378 cm-1, which coincide with the peak positions of three species themselves. C—H methylene symmetric stretching around 2 854 cm-1, C—O stretching of aliphatic aldehydes at 1 233 cm-1 and long-chain C—H methylene bending at 729 cm-1 have the same embodiment between wood wax oil and three surface-coated species. The above results indicate that the characteristic peaks of infrared spectra of three species are not affected by wood wax oil. Correlation coefficient between three species themselves and three surface-coated samples can also confirm it. (2) The FTIR spectrum can distinguish P. tinctoricus Welw from Pterocarpus santalinus and Dalbergia louuelii at 1 595, 1 060 and 836 cm-1; The SDIR spectrum can distinguish Dalbergia louuelii from 1 551 cm-1 and can further verify the characteristic peak of P. tinctoricus Welw; For the 2D-IR spectrum, in the range of 1 425~1 800 and 850~1 300 cm-1, the automatic front of Pterocarpus santalinus is obviously different from the other two species, and the absorption peak attributed to the ether compound at 1 250 cm-1 can separate Pterocarpus santalinus. Redwood identification mainly uses wood anatomy and Surface finishing is mostly concentrated on the study of wood color change. This article makes the best of infrared spectroscopy. Finally, Functional group differences with characteristic peaks of tree species and wood wax oil can directly speculate different content of characteristic components and the specific substances of characteristic components are not required to determine. It is possible to accurately and quickly distinguish the Pterocarpus santalinus painted with wood wax oil and P. tinctoricus Welw and Dalbergia louuelii with which people are confused.
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