A new simple and fast noncovalent coating method based on poly(1-vinylpyrrolidone-co-2-dimethylaminoethyl methacrylate) copolymer was developed for CE. Merely 2 min flushing of the capillary with the poly(1-vinylpyrrolidone-co-2-dimethylaminoethyl methacrylate) copolymer was required. The copolymer is adsorbed onto the fused-silica surface by hydrogen bonding and electrostatic interactions. EOF was almost totally suppressed over a wide pH range. The coating conditions (flushing time, copolymer concentration, and the concentration and pH of background electrolyte solution) and the stability of the coating were optimized, and the coated capillary was successfully applied to the fast separation of four basic proteins: lysozyme, cytochrome c, ribonuclease A, and alpha-chymotrypsinogen A. Separation efficiencies were high, ranging from 386 000 to 738 000 plates/m at 40 mM pH 4.0 acetate buffer being comparable to values obtained on classical covalent PVP-coated capillary. The RSD of migration times of basic proteins for 200 times successive runs were all below 1.0% (n=200, 3 days). A successful capillary performance was demonstrated also to the separation of low- and high-density lipoproteins at acidic pH.

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A new method was developed for the coating of fused-silica capillaries with human high-density lipoproteins (HDLs) for use in electrochromatography. The HDL particles used for the coating differed in particle shape and composition. Both discoidal and spherical particles formed a monolayer on the inner silica wall as confirmed by atomic force microscopy. The effect of coating conditions, such as HDL concentration and coating time, was investigated with spherical HDL particles. Examination of the influence of pH on the coating stability also allowed the determination of pI values for the HDL particles attached to the capillary wall. The pI values for spherical and discoidal HDL particles were close to 5.0. The repeatabilities of the EOF mobility and the retention factors of the uncharged steroid hormones used as model compounds were exploited in the evaluation of the coating stability. The optimal coating was achieved with 0.1 mg/mL HDL protein and 50 min flushing with coating solution followed by 15 min standing time. Electrochromatography with HDL-coated open tubular capillaries offers a new tool for the study of HDL particle structure and transformations.

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