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K. Manolidi, E. Rosenberg, N. Thomaidis:
"Method development for the analysis of natural organic dyestuffs by HPLC/DAD and HPLC/MS";
Poster: IMA 2013 - Instrumental Methods of Analysis, Thessaloniki, Greece; 15.09.2013 - 19.09.2013.

An analytical method has been developed that allows the determination of relevant organic compounds that represent or are associated with natural organic dyestuffs as these have been used in antiquity to dye wool, other fibers and textiles. Starting from standard solutions and extracts of dyeing matter, HPLC separations have been developed that allow the characterization of these compounds by HPLC/DAD and HPLC/MS with good resolution and in reasonable time. UV/Vis and MS spectra have been recorded to create a library of spectra of relevant constituents of natural organic dyestuffs.
In parallel to this work, practical experiments were performed in which wool fibers were dyed based on historical and modern recipes. Using these fibers, extraction experiments were performed, which aim at preserving the integrity of the natural organic dyestuff as far as possible, while being as efficient as possible at the same time. More specifically, the eleven different, commercially available dyeing matters that were used for the dyeing experiments, and subsequently extracted and analyzed are the following: Apricot, Elderberry blue, Mango, Anthracite, Olive green, Mistle green, Mignonette yellow, Lac, Nut brown, Catechu russet and Indigo. They are to be used as mordant dyes with the exception of Indigo, which is a vat dye. A mordant dye is a coloring matter that is soluble in water and can be bound to a textile material for which otherwise it has little or no affinity by the addition of a mordant. On the other hand, a vat dye has to be reduced and transformed into a soluble but colorless leuco-form in which the fiber or textile is impregnated. After re-oxidation in air, the dyestuff becomes insoluble again and precipitates on the fiber, yielding its original colour [1]. Different extraction methods were tested that have been proposed in previous studies [2, 3], while we have introduced some variations and improvements to these procedures, concerning the extraction solution and the reconstitution solvent.
Finally, ten different samples obtained from museums, namely Weld, Safflower yellow, Safflower red, Henna, Brazilwood, Madder, Rubia munjistin, Rubia peregrina, Kermes and Mexican cochineal, were extracted with the most efficient extraction methods and analyzed with the optimized HPLC/DAD/MS method.

References
[1] Judith H. Hofenk de Graaf, The colourful past. Archetype Publications, London (2004).
[2] A. Manhita, T. Ferreira, A. Candeias, C. Barrocas Dias, Anal. Bioanal. Chem. 400 (2011) 1501-1514.
[3] L. Valianou, I. Karapanagiotis, Y. Chryssoulakis, Anal. Bioanal. Chem. 395 (2009) 2175-2189.