1-Butyl-3-methylimidazolium-based ionic liquids and an anionic surfactant: Excellent background electrolyte modifiers for the analysis of benzodiazepines through capillary electrophoresis

Hsiu Li Su, Wan Chun Kao, Kuan Wen Lin, Cheng yu Lee, You-Zung Hsieh*

*Corresponding author for this work

Research output: Contribution to journalArticle

25 Scopus citations

Abstract

In this study, we found that adding 1-butyl-3-methylimidazolium-based ionic liquids (ILs) and sodium dodecyl sulfate (SDS) as modifiers in the background electrolyte (BGE) for capillary elec-trophoresis enhanced the separation of benzodiazepines. In particular, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([BMIM][NTf2]) was the best IL additive for the separation system because its anionic moiety interacted favorably with the benzodiazepines. We added SDS because of its known effect on the separation of hydrophobic analytes. We optimized the separation conditions in terms of the concentrations of the IL, SDS, and organic solvent, the pH, and the BGE's ionic strength. The optimal BGE, containing 170 mM [BMIM][NTf2] and 10 mM SDS, provided baseline separation, high efficiency, and satisfactory peak shapes for the benzodiazepines. The separation mechanism was based on heteroassociation between the anionic moiety of the IL and the benzodiazepines, with SDS improving the resolution of the separation. The limits of detection for the seven analytes ranged from 2.74 to 4.42 μg/mL. We subjected a urine sample to off-line solid phase extraction (SPE) prior to the analysis of its benzodiazepine content. Our experimental results reveal that the combination of [BMIM][NTf2] and SDS provides adequate separation efficiency for its application to CE analyses of benzodiazepines after SPE concentration.

Original languageEnglish
Pages (from-to)2973-2979
Number of pages7
JournalJournal of Chromatography A
Volume1217
Issue number17
DOIs
StatePublished - 1 Jan 2010

Keywords

  • 1-Butyl-3-methylimidazolium
  • Benzodiazepine
  • Bis(trifluoromethanesulfonyl)imide
  • Capillary electrophoresis
  • Ionic liquids

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