Elsa Vanker
Sigrid Selberg

Our group recently published a new article Non-invasive analysis of natural textile dyes using fluorescence excitation-emission matrices, Talanta, 2022, 123805 led by Sigrid Selberg and Elsa Vanker.

In this study, multidimensional front-face fluorescence spectroscopy measured from surfaces using a fiber optic probe was assessed as a non-invasive and non-destructive method for the analysis of components in natural textile dyes. Multidimensional fluorescence data was acquired for a collection of wool yarns dyed with natural dyes (31 dyed wool yarn samples that were self-dyed with 18 different natural dyes) that were used as references in a case study of two historical textiles for which liquid chromatography-mass spectrometry was used as a confirmatory technique.

Self-dyed reference yarns
Selection of characteristic EEMs of self-dyed reference samples

Natural dyes are multicomponent mixtures and can originate from different sources (e.g., plants, insects, and fungi). Due to their complex chemical composition and the inherent lability (photooxidative fading and bleaching), the analysis of natural dyes can be quite challenging and in order to analyze dyes on textiles, it is often best to combine different analytical methods.  However, for the analysis of dyes, common and often the most informative methods, like chromatographic separations coupled with different detectors, are all invasive/destructive. The aim of this work was to explore the potential and limitations of fluorescence spectroscopy in analyzing natural dyes from dyed wool yarns using EEMs (excitation-emission matrices), measured directly from the surface of the objects, non-destructively and without any sample preparation.

To demonstrate the utility of the fluorescence method, analysis was conducted on two case study samples – fibers from historical artifacts. Comparing the EEMs of the reference yarns with our unknown case study samples, we were able to identify that dye from a plant of the Rubiaceae family (bedstraws and madders) was used for dyeing the case study samples. 

Here you can find the 50-day free access to the article.

One of the case study objects; Tapestry “Solomon is receiving a bride. Solomon Court” (year of production 1547); Textile sample was obtained from the Conservation and Digitization Centre Kanut (Estonia).

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