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Successful establishment of MEKC with electrochemiluminescence detection based on one functionalized ionic liquid

Xu, Yuanhong, Fang, Lanyun, Wang, Erkang
Electrophoresis 2009 v.30 no.2 pp. 365-371
additives, buffers, detection limit, electrodes, electrolytes, electron transfer, electrophoresis, electrostatic interactions, hydrophobic bonding, hydroxyproline, ionic liquids, micellar electrokinetic capillary chromatography, poisoning, proline, solutes
Herein, one water-soluble functionalized ionic liquid, 1-butyl-3-methylimidazolium dodecyl sulfate ([BMIm⁺][C₁₂H₂₅SO⁻ ₄]), was designed and its superiorities either used as supporting electrolytes or as additives for successful establishment of MEKC with electrochemiluminescence (ECL) detection (MEKC-ECL) method were investigated. Compared with the common supporting electrolytes such as phosphate solution, 1-butyl-3-methylimidazolium dodecyl sulfate solution used as running buffers led to greatly enhanced ECL intensities and column efficiencies for negative targets, a little increase for neutral-charge ones while maintained nearly unchanged for positive ones due to the electrostatic forces between the large cation BMIm⁺ and the solutes and the hydrophobic interactions resulting from the large anion C₁₂H₂₅SO⁻ ₄. Moreover, resolution efficiency between analytes was significantly improved. As the existence of ionic liquid moiety, BMIm⁺, accelerated the electron transfer at the electrode surface, the poisoning effect of long chain C₁₂H₂₅SO⁻ ₄ on the electrode surface was eliminated and reproducible ECL intensities with relative standard derivation of 1.02% (n=6) were obtained. The proposed novel MEKC-ECL system was again validated by the baseline separated two similar amino acids of proline and hydroxyproline with lower detection limits of 0.5 and 0.8 μM (S/N=3), respectively.