Yeonhee Lee oral presentation (OA2-Mon4-3-2)
Molecular Identification of Asian Lacquers from Different Vegetal Origins Using ToF-SIMS
Korea Institute of Science and Technology, Hwarangno 14-gil5, Seongbuk-gu, 02782 Seoul, Korea, Republic of
Traditional Asian lacquers are natural products that have been used as surface coating materials for thousands of years to protect and decorate wooden, leather, paper, metal, and ceramic objects. Lacquers can maintain highly valued properties, including beauty, gloss, and durability for a long period of time. Asian natural raw lacquers are collected from three main lacquer trees: Rhus vernicifera from Korea, China, and Japan; Rhus succedanea in Vietnam and Taiwan; and Melanorrhoea usitata from Thailand and Myanmar. The sap from the three lacquer trees is mainly composed of substituted catechols (60-65%), varying depending on the plant of origin. The substituted catechol composition of sap is different in all of these trees, i.e., urushiol derivatives in Rhus vernicifera, laccol in Rhus succedanea, and thitsiol in Melanorrhoea usitata [1,2].
Pyrolysis-chromatography/mass spectrometry (Py-GC/MS) is a technique of choice to study such insoluble polymeric systems. The pyrolysis step of Py-GC/MS technique generates the thermal decomposition of the framework and produces small pyrolytical fragment markers of lacquer films easy to analyze by GC/MS . However, Py-GC/MS has a limitation to identify molecular compositions of lacquer species. In this study, several chemical markers of vegetal species in Asian lacquers were identified using a methodology consistent with the sampling restrictions required for cultural-heritage objects. Surface analytical methods such as ToF-SIMS, XPS, and FT-IR were used to characterize Korean, Japanese, Chinese, Vietnamese, and Myanmarese lacquers, avoiding time-consuming and destructive processes. The ToF-SIMS results provided the structural characterization of a series of catechol derivatives. The ToF-SIMS spectra of Rhus vernicifera from Korea, Japan, and China, Rhus succedanea from Vietnam, and Melanorrhoea usitata from Myanmar indicated a series of urushiol, laccol, and thitsiol repeat units in the mass range of m/z 0-1800, respectively. This paper provides the identification of several molecular species of vegetal species of Asian lacquers with the aim at providing a methodology necessarily applied in the field of cultural heritage.
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