Fig. 4

UV–vis spectra associated with madder, recorded during HPLC–DAD analysis of a standard alizarin (orange line; retention time: 22.0 min) and sample AP125-1 (blue line; retention time: 21.8 min). Despite similarities with the spectrum of alizarin, the spectra from b sample AP125-1 (retention time: 21.9 min) and c sample AP125-1 (retention time: 22.0 min), the differences in wavelengths show that these spectra do not correspond to alizarin and thus are not indicative of the presence of madder