A sulfonated methacrylate monolithic polymer has been synthesized inside fused-silica capillaries of diameters 50-533-microm i.d. and coated with 65-nm-diameter fully functionalized quaternary ammonium latex particles (AS18, Dionex Corp.) to form an anion-exchange stationary phase. This stationary phase was used for ion-exchange capillary electrochromatography of inorganic anions in a 75-microm-i.d. capillary with Tris/perchlorate electrolyte and direct UV detection at 195 nm. Seven inorganic anions (bromide, nitrate, iodide, iodate, bromate, thiocyanate, chromate) could be separated over a period of 90 s, and the elution order indicated that both ion exchange and electrophoresis contributed to the separation mechanism. Separation efficiencies of up to 1.66 x 10(5) plates m(-1) were achieved, and the monoliths were stable under pressures of up to 62 MPa. Another latex-coated monolith in a 250-microm-i.d. capillary was used for in-line preconcentration by coupling it to a separation capillary in which the EOF had been reversed using a coating of either a cationic polymer or cationic latex particles. Several capillary volumes of sample were loaded onto the preconcentration monolith, and the analytes (inorganic anions) were then eluted from the monolith with a transient isotachophoretic gradient before being separated by electrophoresis in the separation capillary. Linear calibration curves were obtained for aqueous mixtures of bromide, nitrite, nitrate, and iodide. Recoveries of all analytes except iodide were reduced significantly when the sample matrix contained high levels of chloride. The preconcentration method was applied to the determination of iodide in open ocean water and provided a limit of detection of 75 pM (9.5 ng/L) calculated at a signal-to-noise ratio of 3. The relative standard deviation for migration time and peak area for iodide were 1.1 and 2.7%, respectively (n = 6). Iodide was eluted as an efficient peak, yielding a separation efficiency of 5.13 x 10(7) plates m(-1). This focusing was reproducible for repeated analyses of seawater.

This paper describes a new detection method that uses a six-potential waveform to detect all amino acids without derivatization. The detection limits are less than 1 pmol for most of the analytes. The anion-exchange separation uses a ternary gradient with water, 0.25 M sodium hydroxide, and 1.0 M sodium acetate. We present results of waveform optimization experiments designed to minimize gradient artifacts and to achieve optimum conditions for the quantitative analysis of common amino acids. Analytical results for protein hydrolysates are discussed and compared with those obtained by cation exchange followed by ninhydrin derivatization and spectrophotometric detection.

A coating process for covalent coupling of fully formed polymers to silane-treated capillaries is described. The coupling process occurs through free-radical sites created on both the silane and polymer during the polymer crosslinking process. Coupling and cross-linking take place simultaneously, resulting in a densely cross-linked layer on the capillary surface. By using this coating procedure, several polymers, such as polyacrylamide (PA), poly-(vinylpyrrolidone) (PVP), and poly(ethylene oxide), were successfully anchored on capillaries treated with silanes such as (methacryloxypropyl)trimethoxysilane (MET), chlorodimethyloctylsilane (OCT), and trimethoxyallylsilane. High-resolution separations of basic proteins with average efficiencies of 500 000 plates/50 cm were achieved using polymer-coated capillaries such as MET-PVP, MET-PA, and OCT-PVP. Similarly, high-resolution separations of milk proteins and hemoglobin variants were achieved by a MET-PVP-coated capillary. In addition to neutral polymers, the above coupling process was also suitable for attaching cationic polymers. Fast and efficient separations of acidic proteins and small inorganic anions were achieved using an acrylamide-based cationic polymer-coated capillary. The coating process described here is easy to implement and results in reproducible, stable capillary coatings for capillary electrophoresis.Capillary electrophoresis (CE) has emerged as an important tool for analyzing biomolecules. The high-efficiency, high-resolution, and automation capabilities of CE make it highly suitable in the routine analysis of proteins, peptides, and even small ions. A major problem encountered in the above separations is the interaction of basic analytes, such as basic proteins, with exposed surface silanol groups on the capillary wall. This interaction results in loss of efficiency and irreproducible separations. Typical approaches in addressing the above problem include working at conditions where the silanol groups are either un-ionized 1 or fully ionized. 2 These conditions, however, entail working at extremes of pH and may be unsuitable for many analytes. Additionally, silica dissolves at extreme pH's, which is another limitation of this approach. 3 Other approaches in addressing the above problem include adding compounds 4-6 that compete with the analytes for interaction sites on the capillary wall. These additives, however, may adversely affect the separation of analytes.Another popular approach includes working with coatings that are either physically adsorbed or chemically attached to the capillary surface. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] These coatings mask the presence of surface silanols and enhance separation efficiency. The adsorbed coatings suffer from limited stability and require repeated replenishment for effective operation. 7 Recently, Gilges et al. 7 showed excellent separation of basic proteins using a poly(vinyl alcohol) (PVA)coated capillary. The polymer coating was achieved by a thermal treatment that immobilized...

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