Identification of Natural and Early Synthetic Textile Dyes with HPLC and UV/Vis-Spectroscopy by Diode Array Detection

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Abstract
The separation and identification of complex mixtures of natural and synthetic textile dyes was investigated using HPLC with diode array detection. Separation was carried out on a reversed phase column with acetonitrile-phosphoric acid gradient elution. The results show that the anthraquinones from madder root and the insect dye cocheneal present in ancient red dyes can easily be distinguished from azo-dyes present in later textile fibres. They further show that for an analysis of the numerous flavones and flavonoles, constituting most of the yellow natural dyestuffs, the combination of HPLC with on-line optical spectroscopy is particularly useful. Even when retention times are identical - as for instance for quercetin and luteolin - the ratio of a mixture can still be estimated by evaluating the ratio-chromatogram.