Ionic liquids based on imidazole for online concentration of catecholamines in capillary electrophoresis

Abstract

Potential possibilities of long-chain ionic liquids based on imidazole (1-dodecyl-3-methylimidazolium chloride and 1-cetyl-3-methylimidazolium chloride) for online sample concentration techniques (field-amplified sample stacking, head-column field-amplified sample stacking, and sweeping) of catecholamines were studied in both capillary zone electrophoresis and micellar electrokinetic chromatography. The use of a high-conductivity sample matrix in sweeping was found to significantly increase the separation efficiency of analyte up to 2 × 10 theoretical plates per meter and remarkably reduce limits of detection for catecholamines up to 50 ng/mL. This approach was shown to be suitable for the determination of trace amounts of catecholamines in biological fluids.

Recent progress of sample stacking in capillary electrophoresis (2016–2018)

“…With UV detection at 242 nm, the LODs for hormones in human urine were between 25 and 100 μg/L. The same authors investigated the possibilities of long‐chain ionic liquids based on imidazole for online sample concentration (FASS, head‐column FASS and sweeping) of catecholamines in CZE and MEKC. Numerous configurations were tested and the optimized systems provided similar LODs as reported in the previously mentioned paper.…”

Molecular‐sieve‐based matrix solid‐phase extraction combined with field‐amplified sample stacking in capillary electrophoresis for the determination of three organic acids in a complex solid matrix

“…In FASS, the difference in the conductivity of the sample and BGE is the most critical factor affecting enrichment effect . Thus, the effect of phosphate concentration in the sample matrix was examined at 0, 2, 5, and 10 mM in our study.…”

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2016–2018)

“…To combine field enhancement with sweeping, the sample is prepared in a low conductivity solution devoid of pseudostationary phase and this solution is injected into the capillary filled with BGE containing a pseudophase. FASS‐sweeping was applied for the determination of catecholamines , steroid hormones , biogenic amines , deferoxamine , and cephalosporin antibiotics . The urine and surface water samples were extracted by LLE and SPE prior to evaporation of the extract to dryness and reconstitution in a low conductiviy sample diluent that was free of pseudostationary phase.…”

“…Ionic liquids were investigated as alternative to the commonly used cationic CTAB pseudostationary phase for the separation of four catecholamines and four steroid hormones . The rational for the use of imidazole‐based ionic liquids was that these molecules offer additional chemical interaction (e.g., π–π and hydrophobic interactions) with the analyte and these interactions can be used to further improve the sensitivity enhancement factor.…”