Separition of steroid hormones by microemulsion electrokinetic chromatography involving ionic liquids

Abstract

Microemulsion electrokinetic chromatography (MEEKC) is a promising method for separating ionic and neutral analytes in the complex matrix, where a microemulsion is used as the background electrolyte. Current work identified the possibility of using hydrophilic ionic liquids (ILs) based on imidazole (C 12 MImCl, C 16 MImCl) as modifiers and surfactants, as well as hydrophobic ILs (C 6 MImBF 4 ) as an “oil” in the microemulsion for the separation of steroid hormones by MEEKC. The factors such as ILs concentration, nature and pH of the background electrolyte, and the ratio of the components of the microemulsion, that influence the efficiency and separation selectivity of analytes were found. Suitable conditions for the complete separation of a model mixture of steroid hormones: cortisol, cortisone, 11-deoxycortisol, 11-deoxycorticosterone, corticosterone were obtained. The analytical characteristics of methods (optimized conditions) for the determination of steroids by micellar and microemulsion electrokinetic chromatography were compared. It was investigated that the addition of 15 mM 2-hydroxypropyl-β-cyclodextrin increases the separation selectivity and reduces the analysis time. The application of the on-line concentration methods made it possible to reduce the detection limits of analytes to 50 ng / ml. The mode for electrophoretic determination of steroid hormones in biological fluids (urine, blood serum) by MEEKC with the use of ionic liquids has been proposed using the previously obtained results. Keywords : imidazolium ionic liquids, steroid hormones, microemulsion electrokinetic chromatography, microemulsion DOI: http://dx.doi.org/10.15826/analitika.2019.23.2.001 (Russian) L.A. Kartsova, E.A. Bessonova, D.O. Moskvichev Saint-Petersburg State University, Institute of Chemistry, 26 Universitetskii prospect, St. Petersburg, Petergof, 198504, Russian Federation