Identification by RP-HPLC-DAD, FTIR, TGA and FESEM-EDAX of natural pigments prepared from Datisca cannabina L

Abstract

In this study, natural pigments from the hemp (Datisca cannabina L.) dye plant were prepared by using KAl(SO4)2·12H2O (alum), FeSO4·7H2O and SnCl2·2H2O mordants. A reversed-phase high performance liquid chromatography (RP-HPLC) with diode array detection (DAD) method was utilized for the identification of dyestuffs in the natural pigments. The dyestuff extractions from the pigments were carried out with 37% HCl/MeOH/H2O (2:1:1 v/v/v) mixture. The pigments were further characterized by ATR-FTIR analysis. It was found that all metals precipitate datiscetin and carbonates. Also results show that the datiscetin–iron complex co-precipitates with glycosides. Thermal degradation of the pigments was determined by thermogravimetric analysis. High char yields were found for all pigments. These char yields are attributed to the high metal chelating capacity of datiscetin. The microstructure and chemical homogeneity of obtained natural pigments were studied by field emission scanning electron microscopy equipped with energy dispersion spectroscopy.