热裂解气相色质谱应用于古代壁画中油类黏合剂的分析

Pyrolysis Gas Chromatography-Mass Spectrometry Applied to Identification of Oils in Ancient Paintings

采用热裂解气相色质谱分析方法,研究了古代壁画中常见的亚麻油、核桃油、罂粟油和桐油4种天然干性油类黏合剂.通过标准干性油老化膜的分析,建立了一种快速、方便的适合于真正古代壁画中油类样品分析的指纹特征峰图谱,并对采自不同年代及不同地区的古代壁画样品进行分析测试,以评估指纹特征峰图谱的可行性.分析时采用了热裂解与甲基化同时进行的技术.分析结果显示,4种干性油的不饱和脂肪酸在成膜后的甲基化产物均为壬二酸二甲酯,离子质量与离子电荷量比值为217,是干性油的特征检测峰.4种油中不同含量的软脂酸和硬脂酸在干性油成膜前后的比值不变,为干性油的甄别提供了可能性.这一研究为国内古代壁画中干性油及其种类的鉴别提供了一种有效的方法.

The siccative oils were identified via pyrolysis gas chromatography-mass spectrometry for linseed oil, walnut oil, poppy oil and tung oil used as binding media in ancient paintings. The finger marker as a convenient and rapid reference for the characterization of real samples was established according to the analysis of aged standard oil layers and evaluated while the simultaneous pyrolysis with methylation derivation technique was adopted. The results indicate that it is possible to identify and distinguish these siccative oils because the unsaturated acid had changed into azelaic due to oxidation and polymerization during the drying process to make the chromatogram of siccative oils have a typical peak of C9 compound （methylated azelaic acid） and provide a finger marker of m/z 217, and the concentration ratio of palmitic acid to stearic acid remains constant with time to facilitate the differentiation of oils. The proposed method is expected to effectively identify individual siccative oils as binding media in ancient paintings.