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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

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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 B2 and D3, and the cationic vitamin B1 was 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 D3 content of a drug treating vitamin D3 deficiency was determined by SF-MEEKC coupled to ESI-MS using 25-hydroxycholecalciferol as an internal standard.

The concept of surfactant-free microemulsion electrokinetic chromatography coupled to electrospray ionization mass spectrometry

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Acknowledgments

The authors thank Tobias Lopian from the Institut de Chimie Séparative Marcoule (ICSM) for SAXS measurements. S.K. thanks the Fonds der chemischen Industrie (FCI) for a scholarship.

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    Authors and Affiliations

    1. Institute of Analytical Chemistry, Chemo- and Biosensors, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany

      Urška Mohorič, Andrea Beutner & Frank-Michael Matysik

    2. Institute of Physical and Theoretical Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany

      Sebastian Krickl, Didier Touraud & Werner Kunz

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    1. Urška Mohorič
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    2. Andrea Beutner
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    3. Sebastian Krickl
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    5. Werner Kunz
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    Correspondence to Frank-Michael Matysik.

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    Additional information

    Published in the topical collection Fundamental Aspects of Electromigrative Separation Techniques with guest editors Carolin Huhn and Pablo A. Kler.

    Andrea Beutner and Sebastian Krickl contributed equally to this work.

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    Mohorič, U., Beutner, A., Krickl, S. et al. 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. Anal Bioanal Chem 408, 8681–8689 (2016). https://doi.org/10.1007/s00216-016-0057-0

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    • DOI: https://doi.org/10.1007/s00216-016-0057-0

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