Raman spectrometry as a screening tool for solvent-extracted azo dyes from polyester-based textile fibres

Some types of textile fibres are considered to be the cause of allergic reactions and other adverse health effects on humans. The main compounds behind these health problems usually contain azo groups in their chemical structure, which are widely employed as azo dyes in the manufacture of textile and clothing products. In this respect, availability of simple analytical procedures for identifying azo groups in textiles is of concern, not only for toxicological studies, but also for clinical and forensic investigations. In this work, conventional Raman spectrometry was assessed as an analytical tool for identification of the azo function in the extracts of fibres obtained after applying a liquid-solvent extraction procedure to the polyester-based textile products. A medium-polarity solvent of ethanol-diethyl ether (1:1 mixture) was shown to be the most effective extraction medium. Two laser lines at 514.5 nm and 785 nm were compared, with the longer wavelength preferred as additional peaks were identified in the Raman spectrum, which had better signal-to-background and signal-to-noise ratios owing to decreased fluorescence in contrast to excitation at 514.5 nm. The method reported is a convenient procedure that can be applied in many instances when rapid screening of fibre dyes is required.