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A TiO2 nanoparticle (TiO2 NP)-coated open-tubular column for the capillary electrochromatographic separation of proteins is described. The surface chemistry of the TiO2 NPs on the inner wall of the fused silica was significantly affected by the running buffer. By varying of the phosphate buffer pH, only cathodic EOF was indicated. The results showed that TiO2 NPs are existed as a complexed form with the buffer ligand. Good separation of conalbumin (ConA), apo-transferrin (apoTf), ovalbumin (OVA), and BSA could be achieved with phosphate buffer (40 mM, pH 8.0) and an applied voltage of 15 kV. Five peaks of glycoisoforms of OVA were observed under these conditions. In comparison with the retention behavior of the analytes on the bare fused-silica column, the new column's high resolving power seems to be predominantly derived from the ligand exchange of the analytes with the phosphate adsorbed onto the TiO2 NPs. The method was also used to separate egg-white proteins. Both acidic and basic proteins in egg white were separated in a single run. The microheterogeneities of OVA could also be found in it. The separation efficiency for the main peak of OVA in egg white was around 10,000 plates/m.

A novel column made through the condensation reaction of TiO2 nanoparticles (TiO2 NPs) with silanol groups of the fused-silica capillary is described. EOF measurements under various buffer constitutions were used to monitor the completion of reactions. The results indicated that the EOF was dependent on the interactions between buffers and the bonded TiO2 NPs. With formate/Tris buffer, EOF reversal at pH below 5 and cathodic EOF at pH above 5 were indicated. The pI of the bonded TiO2 NPs was found at approximately ph 5. Only cathodic EOF was illustrated by substituting the mobile phase with either glutamate or phosphate buffer. It was elucidated that both glutamate and phosphate buffer yield a negative charge layer on the surface of TiO2 NPs attributable to the formation of a titanium complex. The CEC performance of the column was tested with angiotensin-type oligopeptides. Some parameters that would affect the retention behavior were investigated. The interactions between the bonded phases and the analytes were explicated by epitomized acid-base functional groups of the oligopepetides and the speciation of the surface oxide in different pH ranges. The average separation efficiencies of 3.1 x 10(4) plates/m is readily achieved with a column of 70 cm (50 cm) x 50 mum ID under an applied voltage of 15 kV, phosphate buffer (pH 6.0, 40 mM), and UV detection at 214 nm.

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A molecularly imprinted polymer (MIP) comprising 9-ethyladenine was polymerized in situ inside the capillary for the electrochromatographic separation of nucleotide bases. The capillary wall was first functionalized with 3-trimethoxysilylpropyl methacrylate (10% v/v) and 1,1-diphenyl-2-picrylhydrazyl (0.01% w/v) in toluene. Following this treatment, the capillary was filled with acetonitrile containing 9-ethyladenine, methacrylic acid, ethylene glycol dimethacrylate, and initiator. After polymerization, the MIP was shrunk into a film against the inner wall of the capillary with the syringe pump. The template was then removed with methanol under nitrogen flow. For evaluation the feasibility of the MIP column for the separation of nucleotide bases, some parameters including the pH, concentration of the background electrolyte, the applied voltage as well as the effect of organic modifier were studied. The migration behavior of nucleotide bases on the MIP column was also compared with that on the bare fused-silica column. The results indicated that the MIP columns demonstrated better recognition properties at a pH range of 6-8. The efficiency (plates/m) at pH 8 for the nonimprinted analyte was 75,300 for cytosine, 50,200 for thymine, and 14,800 for guanine. However, the efficiency for the imprinted analyte, adenine, was quite low. This was evidenced by the broad peak, yielding only 2600 plates/m.