This PhD thesis aims at characterising dyes in historical and archaeological textiles by using chromatographic and mass spectrometric techniques (High Performance Liquid Chromatography with UV-Visible, Diode Array and Mass Spectrometric detector, Gas Chromatography / Mass Spectrometry and Direct Exposure – Mass Spectrometry). The analytical techniques used are evaluated in terms of sensitivity, selectivity and repeatability and are validated by analysing reference materials, both prepared in laboratory and kindly provided by experts of dyeing with natural sources. Electrochemical methods (cyclic voltammetry and controlled potential bulk electrolysis) are used for clarifying oxidation reactions of selected chromophores.
Particularly, Chapter 2 presents a review of the literature with regard to the characteristics of organic dyes and to the analytical methods used for their identification in textile samples of historical importance. Chapter 3 describes the materials and instrumentation used throughout the experimental work. In Chapter 4 and 5 the main analytical problematic connected with dye analysis are addressed and possible solutions are presented. Particularly, the following issues are discussed: the improvement of analytical techniques in terms of detection limits and reproducibility, in order to obtain reliable information notwithstanding the small amount of sample available for analysis; the development of methods applicable to the wide range of compounds used as molecular markers of dyestuffs; the characterisation of matrix components and the evaluation of their effects on the analysis of dyestuffs; the study of degradation processes. Moreover, in Chapter 5, results obtained with electrochemical methods with regard to the redox properties of some flavonoid chromophores are described. Chapter 6 presents a number of case studies: the developed analytical techniques were applied to the characterisation of archaeological and historical textiles. Although the amount of sample available was in most cases extremely low, the application of the optimised sample treatment allowed for efficiently extracting chromophores belonging to several chemical classes from unique micro samples. At the same time, the application of complementary chromatographic techniques, in some cases assisted by morphological and elemental analysis, enabled for achieving a complete picture of the analysed objects.