Identification of yellow dyes in two wall coverings from the Palace Museum: Evidence for reconstitution of artifacts

Glycosylated flavonols were characterized in the extracts of Rhamnus petiolaris and Rhamnus utilis, by high performance liquid chromatography coupled with photo diode and mass spectrometric detectors (HPLC-PDA-MS). The main dye components are rhamnetin-3-O-rhamninoside for R. petiolaris and kaempferol-3-O-rhamninoside for R. utilis. Based on this information, the yellow dye used in the wall cloth in the Palace Museum can be identified as R. petiolaris or a closely related species. In the case of the wallpaper (which was under the wall cloth), the main flavonoid found was rutin, suggesting that it was dyed with buds of pagoda tree (Sophora japonica), a dye traditionally used in China. The results presented here provide valuable information in regard to reconstitution of the late Qing dynasty (1840-1912 AD) wall coverings. In addition to HPLC-PDA-MS analysis, surface enhanced Raman spectroscopy (SERS) was used to tentatively identify yellow dyes in the two historical artifacts. Only a 1 mm length of single fiber, obtained from each Qing dynasty sample, was needed for comparison with the SERS data of dye references. This ultra-sensitive method is suitable for situations where sampling is restricted to trace amounts.