title: Extracting natural dyes from wool--an evaluation of extraction methods.
abstract: 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 Na(2)EDTA 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(2)EDTA/DMF extraction of the wool embroidery samples and an LC-DAD-MS methodology. The effectiveness of the Na(2)EDTA/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.
authors.affiliation: Chemistry Department and Évora Chemistry Centre, University of Évora, Rua Romão Ramalho 59, 7000-671 Évora, Portugal.
authors.forename: Ana
authors.initials: A
authors.lastname: Manhita
authors.forename: Teresa
authors.initials: T
authors.lastname: Ferreira
authors.forename: António
authors.initials: A
authors.lastname: Candeias
authors.forename: Cristina Barrocas
authors.initials: CB
authors.lastname: Dias