CAPILLARY ION CHROMATOGRAPHY WITH ONLINE HIGH-PRESSURE ELECTRODIALYTIC NAOH ELUENT PRODUCTION AND GRADIENT GENERATION

A small inexpensive system is described that allows high-performance s uppressed anion chromatography on a capillary scale, A fully computer- controlled stepper motor-driven syringe-type dispenser, equipped with a 500 mu L-capacity glass syringe is capable of pumping at pressures u p to 1000 psi when equipped with an appropriate inlet check valve. Fus ed-silica capillary columns similar to 50 cm in length and 180 mu m i. d., packed in-house with a commercial packing, provide excellent perfo rmance, significantly exceeding the efficiencies observed for the same packing in commercially available 2 mm bore format, The system operat es with a pressure drop of <800 psi at a now rate of 2 mu L/min. The s ystem utilizes a novel electrodialytic NaOH eluent generator that is d eployed on the high-pressure side of the pump and thus requires no spe cial measures for electrolytic gas removal, This device permits both i socratic and gradient operation with excellent eluent purity; the NaOH concentration is generated linearly with applied current with near-Fa radaic efficiency, up to a concentration of at least 100 mM.