A multi-functional open-tubular (OT) column covalently modified with [3-(phenylamino)propyl]trimethoxysilane (PPTMS) via a single-step silanization reaction has been developed, and employed for alkaloids and aromatic acids analytes by CEC. Both anodic and cathodic EOF could be gained in the PPTMS-bonded column, and anodic EOF was exhibited when the pH of running buffer was less than 8.0. Using thiourea as the EOF marker, a satisfactory column stability was denoted, and the RSD values for migration time and peak area were gained at 0.5 and 3.7% (intra-day, n=5), 1.7 and 5.6% (inter-day, n=3), 3.9 and 5.8% (column-to- column, n=16 in four batches). With anodic EOF mode (pH=2.0 of 10 mmol/L phosphate buffer), favorable separations of cationic alkaloids (viz. uridine, adenosine, cytidine, adenine, cytosine) were successfully achieved with column efficiencies ranging from 95 000 to 187 000 plates/m, and the undesired adsorption on the inter-wall of capillary column could be avoided. Besides, six anionic aromatic acids could be also separated efficiently in the co-electroosmotic mode with anodic EOF. And high efficiencies ranged from 176 000 to 235 000 plates/m were gained with a good repeatability. PPTMS-bonded capillary column might be used as an alternative functional medium to physical coating capillary column for the analyses of aromatic organic acids and bases.

The interaction of a novel bioactive agent N-{[N-(2-dimethylamino) ethyl] acridine-4-carboxamide}-α-alanine [N-(ACR-4-CA)-α-ALA] with human serum albumin (HSA) was investigated by fluorescence spectroscopy, UV–vis absorption and circular dichroism spectrophotometric techniques under simulative physiological conditions. The fluorescence quenching of HSA by addition of N-(ACR-4-CA)-α-ALA is due to static quenching and hydrogen bonding. Moreover, hydrophobic interactions play a role in the binding of N-(ACR-4-CA)-α-ALA to HSA as well. The number of binding sites, n, and the binding constant values, K_A, were noted to be 0.88 and 3.4 × 10⁴ L mol⁻¹ for N-(ACR-4-CA)-α-ALA at 293 K. The binding distances and the energy transfer efficiency between N-(ACR-4-CA)-α-ALA and protein were determined. The negative value of enthalpy change and positive value of entropy change in the present study indicated that both hydrogen bonding and hydrophobic forces played a major role in the binding of N-(ACR-4-CA)-α-ALA to HSA. Copyright © 2010 John Wiley & Sons, Ltd.

Molecularly imprinted polymer (MIP) monoliths with (S)-ornidazole ((S)-ONZ) as the template molecule have been designed and prepared by the simple thermal polymerization of methacrylic acid, 4-vinylpyridine, and ethylene dimethacrylate in the presence of a binary porogenic mixture of toluene and dodecanol. The influences of polymerization mixture composition on the chiral recognition of ONZ have been evaluated, and the imprint effect in the optimized MIP monolith has been clearly demonstrated. The new monolithic stationary phase with optimized porous property and good selectivity was used for the chiral separation of ONZ by pressurized CEC. The pressurized CEC conditions were also optimized to obtain the good chiral separation. The enantiomers were rapidly separated within 9 min on the MIP-based chiral stationary phase, whereas the chiral separation was not obtained on the nonimprinted polymer. Additionally, the proposed method has been successfully applied to the chiral separation of ONZ in tablet samples by injection of the crude sample. The cross-selectivity for similar antiparasitic drug was investigated. The results indicated that the chiral separation of secnidazole could also be obtained on the optimized MIP monolith within 14 min.

A method was developed to quantify domoic acid (DA), the chemical responsible for amnesic shellfish poisoning (ASP), by pressurized CEC (pCEC). The effect of different experimental conditions on the separation of DA and matrix solutes, such as the content of ACN in mobile phase, pH and concentration of buffer, supplementary pressure and applied voltage, were investigated. Under the optimal conditions, the pCEC method separated DA from shellfish matrices within 6 min. By using supplementary pressure, bubble formation in the capillary column was completely suppressed. The method was repeatable, sufficient accurate and sensitive for rapid screening of DA in shell seafood.

A novel zwitterionic monolith was prepared by in situ covalent attachment of glycin to a γ-glycidoxypropyltrimethoxysilane-modified silica monolith. The monolith possessing in its structure bonded secondary amine groups and carboxylic acid groups was evaluated in pressurized CEC (pCEC) system using small neutral and charged solutes. Owing to the zwitterionic nature of the resulting stationary phase, the direction and magnitude of EOF in this column could be manipulated by adjusting the pH values of the mobile phase. Typical hydrophilic interaction was observed when the ACN content exceeded 45%. Separations of acidic and basic compounds were performed on the prepared column in weakly anodic and cathodic EOF modes, respectively. The organic solvent composition, the salt concentration, and the pH of the mobile phase have effects on the electrochromatographic retention. Besides the hydrophilic interaction and electrophoretic mechanism, electrostatic interactions are also involved in the separations of acids and bases on the zwitterionic column.

A novel silica monolithic stationary phase functionalized with 3-(2-aminoethylamino)propyl ligands for pressurized CEC has been presented. The monolithic capillary columns were prepared by a sol-gel process in 75 μm id fused-silica capillaries and followed by a chemical modification. The diamino groups on the surface of the stationary phase are meant to generate the chromatographic surface and a substantial anodic EOF as well as to provide electrostatic interaction sites for charged solutes. The electrochromatographic characterization and column performance were evaluated by a variety of neutral and charged solutes. It was observed that the anodic EOF for the diamine-bonded monolith was greatly affected by the reaction time with 3-(2-aminoethylamino)propyltrimethoxysilane and the PEG amount in the sol-gel reaction mixture in addition to the mobile phase conditions. The monolithic stationary phase exhibited hydrophilic interaction chromatographic behavior toward neutral solutes. Good separations of various solutes including phenols, nucleic acid bases, nucleosides and nucleotides were achieved under different experimental conditions. Fast and efficient separations were obtained with high plate counts reaching more than 130 000 plates/m.