Separation of metal ions via capillary electrophoresis using a pseudostationary phase microfunctionalized with carbon nanotubes

Simultaneous determination of five metal ions by on-line complexion combined with micelle to solvent stacking in capillary electrophoresis

A direct on-line complexion combined with micelle to solvent stacking method was proposed for simultaneous determination of metal ions by capillary electrophoresis coupled diode array detector. During the experiment, a plug of complexing agent was first injected to the inlet of capillary, followed by introducing the micelle-bound metal ions. Then the metal ions produced a micelle-to-solvent stacking effect and interacted with the complexing agent under a positive voltage. Continued application of voltage, the analytes were effectively focused and separated in the capillary zone electrophoresis. Repeatability was ranged from 1.89% to 1.94% for the migration time. The detection limits were 2.66-27.9 ng mL^-1 for Ni²⁺, Co²⁺, Cu²⁺, Hg²⁺ and Cd²⁺. Furthermore, the developed method showed a great potential for the determination of metal ions in the crayfish, beebread and Dendrobium officinale samples.

Recent advances in nanomaterial-based capillary electrophoresis

This review gives a summary of applications of different nanomateials, such as gold nanoparticles (AuNPs), carbon-based nanoparticles, magnetic nanoparticles (MNPs), and nano-sized metal organic frameworks (MOFs), in electrophoretic separations. This review also emphasizes the recent works in which nanoparticles (NPs) are used as pseudostationary phase (PSP) or immobilized on the capillary surface for enhancement of separation in CE, CEC, and microchips electrophoresis.

CE with multi-walled carbon nanotubes (MWCNTs). Part II. SDS coated functionalized MWCNTs as pseudo-stationary phases in nanoparticle EKC - Retention behaviors of small and large solutes

In this study, functionalized multi-walled carbon nanotubes (MWCNTs), namely hydroxylated MWCNTs (MWCNT-OH), carboxylated MWCNTs (MWCNT-COOH) and sulfonated MWCNTs (MWCNT-SO₃H) coated with sodium dodecyl sulfate (SDS) were demonstrated as effective pseudo-stationary phases (PSPs) in the separation of various species by the nanoparticle capillary electrokinetic chromatography (NPEKC) mode of capillary electrophoresis (CE). Due to the significant increase in their surface charge density in the presence of SDS, the three SDS coated MWCNTs yielded high performance separation for herbicides, barbiturates, dansyl-DL-amino acids (Dns-AAs), dipeptides and proteins by NPEKC. In addition, high resolution tryptic peptide maps of three standard proteins including myoglobin, cytochrome C and lysozyme were readily obtained. The three PSPs systems yielded high plate numbers that spanned a wide range of values depending on the type of species. The values of the observed selectivity factors (i.e., α values) were significantly different among the three PSPs for solutes that underwent strong interactions with the SDS coated functionalized MWCNTs while for negatively charged solutes (e.g., Dns-AAs) of the same charge sign as the PSPs the α values were about the same on the three different PSPs indicating weak association with the PSPs and signaling separation based chiefly on the differences in electro-migration arising from differences in charge-to-mass ratios.

Enantiomeric separation of adrenaline, noradrenaline, and isoprenaline by capillary electrophoresis using streptomycin-modified gold nanoparticles

Enantiomeric separations of the adrenergic compounds adrenaline, noradrenaline, and isoprenaline were studied. Electromigrative separations were performed in uncoated fused silica capillaries using streptomycin-modified gold nanoparticles (ST-AuNPs) as an additive to the background electrolyte. The ST-AuNPs are shown to serve as an effective chiral selector. The modified AuNPs were characterized in terms of size and zeta potential, and by IR and UV-vis spectra. The effects of ST-AuNP concentration, pH value, temperature, and separation voltage on the separations were systematically studied. Under optimized experimental conditions, racemic mixtures of the respective adrenergic drugs were baseline-separated within 7 min with a resolution of up to 7.5. The relative standard deviations of the resolution in inter-day and intra-day studies (n = 5) were generally <5%. Graphical abstract Schematic of the method for enantiomeric separations. (A): At low concentrations of streptavidinylated gold nanoparticles (ST-AuNPs), the better matching enantiomer is preferably "transported" by the ST-AuNPs; (B) ST-AuNP concentration increased to an optimal value; (C): The ST-AuNP concentration is too high; even poorly matching enantiomers will be transported simultaneously.