Metallomesogenic stationary phase for open‐tubular capillary electrochromatography

Abstract

A synthetic coppermesogenic polymer is prepared and then covalently bonded to the siloxane-based deactivated column as the stationary phases of open-tubular CEC with essentially high phase ratio. The EOF generated from the modified phase is surveyed through conventional aqueous buffers and hydroorganic mobile phases. Zeta potentials, which are computed from the EOF data and the ratio of dielectric constant to viscosity, are plotted as a function of pH, ionic molarity, and compositional range. These plots responsible for the electroosmotic characteristic of the bonded phases are found to be like those of bare fused-silica or deactivated columns through decreasing or increasing the ACN content in the mobile phase, respectively. This two-phase characteristic is basically derived from the polymeric configuration with carboxylato ligands attached onto the polysiloxane backbone. Phthalates and amino acids are suitable probes to examine the two phenomena, more-polar and less-polar mediums, respectively, and to judge whether the chromatographic retention is the major source of separation mechanism. With the mixing modes of Lewis acid-base interaction, dispersive force, and shape discrimination, the chromatographic partition adequately accomplishes the uneasily resolved separations by only CZE mode, although the electrophoretic migration is truly somewhat involved.

Multi‐walled carbon nanotube composites with polyacrylate prepared for open‐tubular capillary electrochromatography

“…4, which shows EOF at a minimum when ACN content is 40-60%. In fact, the concave shape of the curve could be found in various OT-CEC formats, specifically, in capillaries prepared by direct polymer coating, by stepwise fabrication, or by in situ polymerization [8,28,40,41]. The m eo values determined by using the neutral solute DMSO did not increase with an increasing ratio of ACN in the eluent, acting as if a reversed-phase chromatography solvent was not present at all.…”

“…Due to concerns about the column lifetime and reproducibility, it is better if the OT-CEC capillaries are modified with covalently attached ligands. Modified capillaries can be produced by the sol-gel approach [6], by stepwise fabrication (usually starting with a silanized capillary) [7], by direct coating with polymers [8], or by the in situ polymerization of functional monomers [9].…”

Novel open tubular CEC with tentacle‐type polymer stationary phase functionalized by phenylalanine

“…The improvement of the resolution is considered due to the enhancement of hydrophobic interaction between the analytes and the stationary phase with increasing the mobile phase ionic strength. If only the hydrophobic interaction was advised, the elution order of the three amino acids should be Trp < Tyr .Phe [10,29]. The elution order of Trp .Tyr .-Phe obtained by using the present column is considered to be effected by a combination of hydrophobic interaction and electrophoretic mobility.…”

“…So far, etched and porous monolith coating capillary columns have been adopted to overcome the intrinsic drawback [8,9]. Moreover, capillary modified with high ligand capacity polymers is considered as an alternative approach [10][11][12]. For example, a tentacle-type metal chelating polymer coating capillary column was fabricated in our laboratory.…”

Recent advances in amino acid analysis by CE

“…The elution times for the aromatic AAs decreased slightly as the ratio of ACN/H 2 O run buffers increased from 50 to 90%. It is noted that ligand exchange should be involved in the separation, which could explain the migration order: Phe, Trp, Tyr [65].…”