Instrumental techniques in the analysis of natural red textile dyes

Various dyes present in historical objects can be indicative of different usage, age and origin of the artifacts. Knowledge about the composition and origin of textile dyes is essential for the preservation and conservation of the items. In this paper, we compare different instrumental techniques to detect and identify natural red dyes from historical textiles without the need for standard substances of the dye components. Several instrumental techniques were used, including liquid chromatography with photodiode array, fluorescence and mass -spectrometric detectors, as well as Fourier transform ion cyclotron resonance mass spectrometry with electrospray ionization and matrix-assisted laser desorption/ionization sources. Seven natural red dye sources were investigated, including dyer's madder, redwood, logwood, sandalwood, kermes, American cochineal and bloodred webcap (Cortinarius sanguineus). The dye components of the latter source have not been characterized before with all of these analytical techniques. A substantial library of chromatograms and mass spectra, along with absorption and fluorescence spectra (altogether 113 chromatograms/spectra), of dyes and/or dye components were recorded and a comparison of the utility of the different analytical techniques in the analysis of the dye sources is provided. The usefulness of the assembled library of chromatograms/spectra is demonstrated on the analysis of several historical textile samples from museum artifacts. (C) 2019 Elsevier Masson SAS. All rights reserved.