Microchemistry and Microscopy Art Diagnostic Laboratory, University of Bologna, Via Guaccimanni 42, 48123 Ravenna, Italy.
Anal Bioanal Chem. 2011 Mar;399(9):3081-91. doi: 10.1007/s00216-010-4388-y. Epub 2010 Nov 11.
This study proposes FTIR spectroscopy in the far-infrared region (FarIR) as an alternative method for the characterisation of natural resins. To this purpose, standards of natural resins belonging to four different categories (sesquiterpenic, i.e. elemi, shellac; diterpenic, i.e. colophony, Venice turpentine; diterpenic with polymerised components, i.e. copal, sandarac; triterpenic, i.e. mastic and dammar) used as paint varnishes have been analysed by FarIR spectroscopy in ATR mode. Discrimination between spectral data and repeatability of measurements have been magnified and verified using principal component analysis, in order to verify the effectiveness of the method in distinguishing the four resin categories. The same samples were analysed in the MidIR range, but the spectral differences between the different categories were not evident. Moreover, the method has been tested on historical samples from the painting "La Battaglia di Cialdiran" (sixteenth century) and from a gilded leather (seventeenth century). In the first case, FarIR spectroscopy allowed confirmation of the results obtained by analytical pyrolysis. In the latter, FarIR spectroscopy proved successfully, effective in the identification of the superficial resin layer that could not be detected with the bulk chromatographic analyses.
本研究提出远红外区（FarIR）的傅里叶变换红外光谱法作为天然树脂特性分析的替代方法。为此，我们对属于四个不同类别（半萜烯类，即埃利姆、紫胶；二萜烯类，即松香、威尼斯松节油；含聚合成分的二萜烯类，即柯巴脂、安息香；三萜烯类，即乳香和达玛脂）的天然树脂标准进行了 FarIR 光谱分析，ATR 模式。使用主成分分析放大和验证了光谱数据之间的区分和测量的可重复性，以验证该方法在区分四个树脂类别方面的有效性。对中红外范围内的相同样本进行了分析，但不同类别之间的光谱差异并不明显。此外，该方法还在绘画作品“Cialdiran 的战斗”（十六世纪）和镀金皮革（十七世纪）的历史样本上进行了测试。在第一种情况下，远红外光谱法证实了热分析结果。在后一种情况下，远红外光谱法成功地证实了其有效性，可用于识别无法通过整体色谱分析检测到的表面树脂层。
