To obtain additional qualitative information about the oxidation pathways involved in the electro-oxidation process of alizarin red, the samples obtained were analysed by UV–vis techniques. The UV spectra of alizarin red, reported in Fig. 6, present one main band in the visible region with a peak at 420 nm and a strong sharp peak in the ultraviolet region at 280 nm that decreased until disappearing, during the electrolysis. Furthermore, the intensity of both bands decreases