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Barrocas Dias C.,HERCULES Laboratory | Barrocas Dias C.,Evora Chemistry Center | Barrocas Dias C.,University of Évora | Miranda M.,University of Évora | And 13 more authors.
Journal of Chemical Education | Year: 2013

Onion skins (Allium cepa L.) and hydrated potassium aluminum sulfate were used to dye wool samples. The main chromophores associated with this natural dye source, quercetin and quercetin-4′-O-glucoside, were identified in the dye bath and in wool extracts by high-pressure liquid chromatography (HPLC) equipped with a diode array detector (DAD) with the help of standards. Two procedures were used to extract dye molecules from dyed wool prior to HPLC-DAD qualitative analysis and the analytical methodology used was discussed in terms of the analysis of historical textile pieces dyed with natural sources. © 2013 The American Chemical Society and Division of Chemical Education, Inc.

Manhita A.,HERCULES Laboratory | Manhita A.,Evora Chemistry Center | Ferreira V.,University of Évora | Vargas H.,Institute of Museums and Conservation | And 10 more authors.
Microchemical Journal | Year: 2011

Wool samples were dyed with madder and alum, copper, and iron salts at different concentration by pre-mordanting (MD) and simultaneous mordanting (M + D) procedures. Samples were artificially aged to identify the influence of the mordant on the madder chromophores photodegradation. A set of analytical techniques was used for complete characterisation of the dyed fibres before and after light exposure, which included colour and chromophore analysis (colourimetry and LC-ESI-MS/MS analysis), determination of mordant ions amounts in the fibres (FAAS and ICP-OES analysis), morphological characterisation of the fibres and punctual chemical analysis (SEM-EDS studies).Fibre colour hue was found to be dependent on the mordant ion nature, mordant bath concentration and dyeing procedure. Mordant ion quantification showed that the uptake of metal ion by the fibres is relatively small, with the Cu ion presenting the highest affinity for the fibre. MD method yields fibres with higher amounts of metal ions and larger chromophore chromatographic peak areas corresponding, in general, to stronger colour hues. Photodegradation was more severe in alum mordant samples and in the first 480. h of light exposure. Chromophore degradation rates are unequal and dependent on the mordant nature, contributing for colour changes observed after light exposure. © 2010 Elsevier B.V.

Manhita A.,University of Évora | Manhita A.,HERCULES Laboratory | Ferreira T.,University of Évora | Ferreira T.,HERCULES Laboratory | And 5 more authors.
Analytical and Bioanalytical Chemistry | Year: 2011

The efficiency of eight different procedures used for the extraction of natural dyes was evaluated using contemporary wool samples dyed with cochineal, madder, woad, weld, brazilwood and logwood. Comparison was made based on the LC-DAD peak areas of the natural dye's main components which had been extracted from the wool samples. Among the tested methods, an extraction procedure with Na2EDTA in water/DMF (1:1, v/v) proved to be the most suitable for the extraction of the studied dyes, which presented a wide range of chemical structures. The identification of the natural dyes used in the making of an eighteenth century Arraiolos carpet was possible using the Na 2EDTA/DMF extraction of the wool embroidery samples and an LC-DAD-MS methodology. The effectiveness of the Na2EDTA/DMF extraction method was particularly observed in the extraction of weld dye components. Nine flavone derivatives previously identified in weld extracts could be identified in a single historical sample, confirming the use of this natural dye in the making of Arraiolos carpets. Indigo and brazilwood were also identified in the samples, and despite the fact that these natural dyes were referred in the historical recipes of Arraiolos dyeing, it is the first time that the use of brazilwood is confirmed. Mordant analysis by ICP-MS identified the widespread use of alum in the dyeing process, but in some samples with darker hues, high amounts of iron were found instead. © 2011 Springer-Verlag.

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