四种黑檀心材的红外光谱差异化与聚类分析

利用红外光谱结合模式识别和二维相关光谱对乌木、东非黑黄檀、风车木和成对古夷苏木四种黑檀硬木心材进行鉴别和聚类分析。红外光谱显示四种木材中的主体成分为纤维素（特征吸收峰位置在~1 370, ~1 158, ~1 034和~895 cm-1附近）、木质素（特征吸收峰位置~2 935, ~1 510, ~1 462和~1 426 cm-1附近）和草酸钙（特征吸收峰位置~1 615, ~1 318和~781 cm-1附近）。三种主体成分在四种木材红外光谱之间的相对峰强度H表明：乌木和东非黑黄檀中木质素含量较高，风车木中草酸钙含量较高，成对古夷苏木中含有一定量的脂类成分。根据红外光谱的差异性选取不同的波段，优选计算参数，分别对四种硬木心材进行相关系数判别分类和SIMCA聚类分析。相关系数判别分类模式识别中，成对古夷苏木中有一个样本未得到有效的验证，但是其余三个木材样品均得到了有效验证。SIMCA聚类模式识别中，四种木材心材之间的识别率、拒绝率和验证率都达到100%，说明不同木材之间没有重叠区域，可以完全的区分识别。二维相关红外光谱中，乌木与东非黑黄檀在升温过程中纤维素的C—O和C—C基团对温度敏感性较高，风车木中草酸钙热敏性较高，成对古夷苏木中木质素的热敏性高于纤维素。红外光谱结合聚类分析和二维相关红外光谱，不仅可以对木材主体成分进行的定性和相对含量的分析，在完善聚类模型基础上还可以对木材种类进行快速、有效的分类模式识别。

Discrimination of Four Black Heartwoods Using FTIR Spectroscopy and Clustering Analysis

A fast discrimination method of four black heartwoods was developed by Fourier Transform Infrared Spectroscopy (FTIR) combining with clustering analysis. In FTIR spectra, the principal chemical components of heartwood were characterized for cellulose (the bands at around ~1 370, ~1 158, ~1 034 and ~895 cm-1), lignin (the bands around ~2 935, ~1 510, ~1 462 and ~1 426 cm-1) and calcium oxalate (peaks at ~1 615, ~1 318 and ~781 cm-1). The correlation coefficient and relative intensity among samples with standard material result that D. ebenum and D. melanoxylon are lignin-rich, while C. imberbe contains more calcium oxalate. G. conjugate has peaked at 1 738 cm-1 means it contains resin. Based on the correlation coefficient, the method of Compare clustering analysis was used to classify four blackwoods. The classification rate was above 95% during blind sample testing. Meanwhile, four blackwood were successfully classified by the method of SIMCA clustering analysis. The recognition rate and rejection rate reached up to 100%. The accuracy of clustering reached up to 100% during blind sample testing. It explained that the four tree species could be classified and identified completely by SIMCA clustering analysis. Besides, cellulose showed high thermal sensitivity in D. ebenum and D. melanoxylon through the 2DCOS-IR synchronous spectra. Calcium oxalate showed high thermal sensitivity in C. imberbe and lignin showed high thermal sensitivity in D. melanoxylon. Combined with cluster analysis calculation and 2DCOS-IR, FTIR can analyze the relative content of the main composition of wood and quickly and effectively classify the pattern recognition of wood species based on the improving clustering model.