Molecular identification of Asian lacquers from different trees using Py-GC/MS and ToF-SIMS

Abstract

Traditional Asian lacquers are natural products with highly valued properties, including beauty, gloss, and durability. Pyrolysis-gas chromatography/mass spectrometry is the technique of choice to study insoluble polymeric lacquer films. In the present study, pyrolysis-gas chromatography/mass spectrometry results showed that the pyrolysis products of lacquer films were different for all of the studied trees, with urushiol derivatives detected in Toxicodendron vernicifluum from China, Japan, and Korea; laccol in Toxicodendron succedaneum from Vietnam; and thitsiol in Gluta usitata from Myanmar. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was also used to characterize the Asian lacquers, avoiding the time-consuming and destructive processes of other techniques. The ToF-SIMS spectra provided structural characterization of a series of urushiol, laccol, and thitsiol derivatives for Tvernicifluum from China, Japan, and Korea; Tsuccedaneum from Vietnam; and Gusitata from Myanmar, respectively. To differentiate the ToF-SIMS results for the different Asian lacquer films, principal component analysis was used because it can extract differences in the spectra and indicate what peaks are responsible for these differences. The results indicate that lacquer films from different lacquer trees can be very different. Therefore, ToF-SIMS with principal component analysis is suitable for the characterization and differentiation of Asian lacquer films in cultural heritage applications.