Microspectrophotometric discrimination of single fibres dyed by indigo and its derivatives using ultraviolet-visible transmittance spectra

Abstract

Single fibres dyed by indigo and its seven derivatives were measured by microspectrophotometric examination of transmittance spectra in the ultraviolet-visible region (240-760 nm). Glycerin was the most suitable embedding reagent for this measurement. Small intra-sample variation of the transmittance intensity in single woollen fibres was observed, but relatively large inter-sample variation was observed among the fibres obtained from different areas in the same textile. There were no differences in the hmax, hmin and the position of shoulders observed in their spectra. This method was applied to the discrimination of single cotton fibres dyed by vat dyes, such as indigo and seven indigo derivatives which had similar structures. On the basis of the ultraviolet-visible transmittance spectra, these sample fibres could be distinguished from one another. It is a non-destructive method compared with chromatographic dyestuff extraction methods; furthermore, utilization of the ultraviolet region gave spectra providing useful information for evaluating fibre evidence.