A small inexpensive system is described that allows high-performance suppressed anion chromatography on a capillary scale. A fully computer-controlled stepper motor-driven syringe-type dispenser, equipped with a 500 μL-capacity glass syringe is capable of pumping at pressures up to 1000 psi when equipped with an appropriate inlet check valve. Fused-silica capillary columns ∼50 cm in length and 180 μm i.d., packed in-house with a commercial packing, provide excellent performance, significantly exceeding the efficiencies observed for the same packing in commercially available 2 mm bore format. The system operates with a pressure drop of <800 psi at a flow rate of 2 μL/min. The system utilizes a novel electrodialytic NaOH eluent generator that is deployed on the high-pressure side of the pump and thus requires no special measures for electrolytic gas removal. This device permits both isocratic and gradient operation with excellent eluent purity; the NaOH concentration is generated linearly with applied current with near-Faradaic efficiency, up to a concentration of at least 100 mM.

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Quantitative reproducibility and separation efficiency in high-performance capillary electrophoresis is often limited by the reproducibility and the nature of the sample introduction procedure. This is particularly true where electrostacking is involved, whether such is deliberately carried out or happens automatically with the choice of ionic strength of the running electrolyte. Extraneous dispersion frequently originates in the act of sample introduction, for example, from the shock of the capillary entering a sample vial or a sample-filled capillary entering the carrier electrolyte source vial. A method based on the stacking of the sample constituents, before the capillary actually contacts the liquid in a vial, can reduce this problem. This technique can be utilized for the preconcentration of sample constituents and to improve separation efficiency by reducing dispersion. In favorable cases, plate counts can increase by as much as 160%, approaching theoretical diffusion-limited efficiencies.

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