Effective separation of organic dyes using ionic liquids as green mobile phase and polyaniline-modified silica gel nanocomposite-based thin-layer chromatography

Background: Organic dyes are used for a wide variety of purposes including their applications in textiles, foods, printing cosmetics and pharmaceuticals. Thus, these are industrially very important and their analysis is always required before putting to particular use. Methods: To develop the extremely efficient thin layer chromatographic system for the resolution of co-existing dyes, the silica gel was modified with the conducting polymer polyaniline. Silica gel and polyaniline modified silica gel were used as stationary phase while the different formulations based on aqueous solutions of ionic liquids such as 1-methyl-imidazolium chloride, 1,2,3-trimethylimidazolium methyl sulphate and 1-ethyl 3-methyl-imidazolium tetrafluoroborate were used as mobile phase to study the migration behaviour of organic dyes. Results: Comparatively better separation efficiency was observed in case of polyaniline modified silica gel with respect to unmodified silica gel. Densitogrpahic presentation of separation of organic dyes achieved using polyaniline modified silica gel (Pani@SG-ES) was also presented. The thin layer chromatographic system comprising of polyaniline modified silica gel (Pani@SG-ES) as stationary phase and 2% aqueous 1methyl-imidazolium chloride as green mobile phase was observed to be most efficient towards separation of several three-component mixtures of organic dyes. The effect of presence of impurities on the efficiency of separation was examined and the detection limits of the dyes were also calculated. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM with EDX) and transmission electron micrograph (TEM) studies were undertaken to characterize silica gel and polyaniline modified silica. Conclusions: A new thin layer chromatographic system consisting of polyaniline modified silica gel (S2) as stationary phase with 2 % aqueous (1-methylimidazolium chloride) as eco-friendly mobile phase is most favourable for the identification and separation of three-component mixtures of organic dyes.