Simple gradient system for capillary electrochromatography

A new gradient system for CEC was designed and adapted to a home-built CEC system. Chromatographic separations are initiated with a predetermined mobi le phase composition and, after a desired time period, a syringe pump deliv ers pure organic solvent at a preset flow rate into a 2 mL vial used as the inlet buffer reservoir. Mixing is achieved by the use of a microstir bar i n the buffer reservoir, which in turn is driven by an air-actuated stir pla te. In this way, a convex-shaped gradient is generated, and the mobile phas e is introduced into the separation column by electro-osmotic flow. Use of this system significantly reduced analysis time while still retaining accep table reproducibility. Nonaqueous CEC was used for isocratic and gradient s eparation (< 3.5% RSD in retention times). Demonstrated applications includ e the analysis of triglycerides in different vegetable oil samples. This sy stem is expected to be well suited for generating other types of gradients, such as pH and ionic strength gradients, in electroseparation techniques. (C) 2001 John Wiley & Sons, Inc.