Ionic liquid as separation enhancer in thin-layer chromatography of biosurfactants: mutual separation of sodium cholate, sodium deoxycholate and sodium taurocholate

Abstract

Background: Physiological biosurfactants plays an important role in digestion of lipids and cholesterol also emulsifies fat-soluble vitamins. Methods: A new green thin-layer chromatographic system comprising ionic liquid (1-methylimidazolium chloride) impregnated silica gel G and 2-methyl tetrahydrofuran as stationary and mobile phases was found to be most suitable for the separation of ternary mixture of biosurfactants (sodium cholate, sodium deoxycholate and sodium taurocholate). The surface structure and chemical composition of silica gel G modified by impregnation with 1-methylimidazolium chloride were examined with the aid of scanning electron microscopy and energy-dispersive X-ray spectrophotometry, respectively. Results: Compared to plain silica gel, enhanced separation efficiency of ionic liquid impregnated silica gel was observed for the resolution of biosurfactants from their mixture. Chromatographic parameters such as ΔRF, separation factor (α) and resolution (RS) for the separation were calculated. Effect of foreign substances (metal cations, inorganic anions, vitamins, amino acids and non-ionic surfactants as impurities) on the separation of surfactants was also examined. Effects of concentration level of 1-methylimidazolium chloride as impregnant and its substitution by other ionic liquids (1,2,3-trimethylimidazoliummethyl sulphate, 1-ethyl-3-methylimidazolium tetrafluoroborate) were also studied to decide the optimum experimental conditions for better separation possibilities. The limits of detection of sodium cholate, sodium deoxycholate and sodium taurocholate were calculated. Conclusion: A new green thin-layer chromatographic system comprising ionic liquid (1-methylimidazolium chloride) impregnated silica gel G and 2-methyl tetrahydrofuran as stationary and mobile phases provide the most suitable environment for the separation of ternary mixture of biosurfactants. [Figure not available: see fulltext.].