Ionic Liquid in Thin-Layer Chromatography of Anionic Surfactants: Selective Separation of Sodium Deoxycholate and Identification in Commercial Products

The coupling of a silica static flat phase impregnated with an ionic liquid (1-methylimidazolium chloride) as stationary phase with 2-methyltetrahydrofuran an alternative green solvent of tetrahydrofuran as mobile phase has been very successful for a selective separation of sodium deoxycholate from other commonly used anionic surfactants. The proposed thin-layer chromatographic system is capable to analytically discriminate among the anionic surfactants in relation to their migration behaviour on an ionic liquid loaded silica layer. The surface structure and chemical composition of silica gel G modified by impregnation were examined with the aid of scanning electron microscopy (SEM) and energy dispersive X-ray spectrophotometry (EDX) respectively. Effects of concentration level of 1-methylimidazolium chloride as impregnant and its substitution by other ionic liquids (1,2,3-trimethylimidazolium methyl sulphate, 1-ethyl-3-methylimidazolium tetrafluoroborate) were also studied to decide the optimum experimental conditions for better separation possibilities. Chromatographic parameters such as ΔRF, the separation factor (α) and the resolution (RS) for the separation and limit of detection were calculated. The developed method has been usefully applied for the identification of sodium deoxycholate and sodium lauryl sulphate in formulated and commercially available products (Colgate toothpaste and Head & Shoulder Shampoo).

Eco-favourable Mobile Phase in Thin Layer Chromatographic Analysis of Surfactants: Resolution of Coexisting Alkyl Dimethylbenzyl Ammonium Chloride, Cetyltrimethyl Ammonium Bromide and Triton X 100

A thin-layer chromatographic system comprising of silica gel as stationary phase and a mixture of methanol, 0.1 % aqueous sodium thiocyanate, acetone and ethyl acetate in 7 : 3 : 2 : 3 ratio as eco-favourable mobile phase has been found most efficient for the separation of ternary mixture of surfactants (alkyldimethylbenzylammonium chloride (ADBAC) + cetyltrimethylammonium bromide (CTAB) + Triton X 100). The separation pattern has been presented as densitogram. Chromatographic parameters like ΔRF, separation factor (α) and resolution (RS) for the separation have been calculated. The effect of the presence of foreign substances such as metal cations, metal anions, amino acids and vitamins as impurities on the separation has been examined. The mobility trend of the separated surfactants was also examined by replacing methanol with other alcohols. The detection limits for ADBAC, CTAB and Triton X 100 have been determined. The proposed method has been successfully applied for the identification of ADBAC in the household cleaning product “Lizol”.