title: Surfactant-free microemulsion electrokinetic chromatography (SF-MEEKC) with UV and MS detection - a novel approach for the separation and ESI-MS detection of neutral compounds.
abstract: Microemulsion electrokinetic chromatography (MEEKC) is a powerful tool to separate neutral species based on differences in their hydrophobic and hydrophilic properties. However, as a major drawback the conventionally used SDS based microemulsions are not compatible with electrospray ionization mass spectrometry (ESI-MS). In this work, a surfactant-free microemulsion (SFME) consisting of water, ethanol, and 1-octanol is used for surfactant-free microemulsion electrokinetic chromatography (SF-MEEKC). Ammonium acetate was added to the SFME enabling electrophoretic separations. The stability of SFMEs containing ammonium acetate was investigated using small-angle X-ray scattering and dynamic light scattering. A method for the separation of a model system of hydrophobic and hydrophilic neutral vitamins, namely the vitamins B2and D3, and the cationic vitamin B1was developed using UV/VIS detection. The influence of the ammonium acetate concentration on the separation performance was studied in detail. The method was characterized concerning reproducibility of migration times and peak areas and concerning the linearity of the calibration data. Furthermore, SF-MEEKC was coupled to ESI-MS investigating the compatibility between SFMEs and the ESI process. The signal intensities of ESI-MS measurements of the model analytes were comparable for SFMEs and aqueous systems. Finally, the vitamin D3content of a drug treating vitamin D3deficiency was determined by SF-MEEKC coupled to ESI-MS using 25-hydroxycholecalciferol as an internal standard. Graphical abstract The concept of surfactant-free microemulsion electrokinetic chromatography coupled to electrospray ionization mass spectrometry.
authors.affiliation: Institute of Analytical Chemistry, Chemo- and Biosensors, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany.
authors.forename: Urška
authors.initials: U
authors.lastname: Mohorič
authors.affiliation: Institute of Analytical Chemistry, Chemo- and Biosensors, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Beutner
authors.affiliation: Institute of Physical and Theoretical Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Krickl
authors.affiliation: Institute of Physical and Theoretical Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany.
authors.forename: Didier
authors.initials: D
authors.lastname: Touraud
authors.affiliation: Institute of Physical and Theoretical Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany.
authors.forename: Werner
authors.initials: W
authors.lastname: Kunz
authors.affiliation: Institute of Analytical Chemistry, Chemo- and Biosensors, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany. Frank-Michael.Matysik@chemie.uni-regensburg.de.
authors.forename: Frank-Michael
authors.initials: FM
authors.lastname: Matysik
mesh_terms: D020003:1-Octanol / Q000737:chemistry; D000085:Acetates / Q000302:isolation & purification; D002112:Calcifediol; D002762:Cholecalciferol / Q000302:isolation & purification*; D020374:Chromatography, Micellar Electrokinetic Capillary / Q000379:methods*; D000067493:Dynamic Light Scattering; D004655:Emulsions; D000431:Ethanol / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D012015:Reference Standards; D015203:Reproducibility of Results; D012256:Riboflavin / Q000302:isolation & purification*; D053838:Scattering, Small Angle; D012996:Solutions / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013831:Thiamine / Q000302:isolation & purification*; D014867:Water / Q000737:chemistry
chemical_list: D000085:Acetates; D004655:Emulsions; D012996:Solutions; D014867:Water; D002762:Cholecalciferol; D000431:Ethanol; D020003:1-Octanol; D002112:Calcifediol; C018824:ammonium acetate; D012256:Riboflavin; D013831:Thiamine
keywords: Electrokinetic chromatography; Electrospray ionization mass spectrometry; Hydrophobic and hydrophilic neutral compounds; MEEKC; Surfactant-free microemulsion