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 mobile phase composition and, after a desired time period, a syringe pump delivers 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 in the buffer reservoir, which in turn is driven by an air-actuated stir plate. In this way, a convex-shaped gradient is generated, and the mobile phase is introduced into the separation column by electro-osmotic flow. Use of this system significantly reduced analysis time while still retaining acceptable reproducibility. Nonaqueous CEC was used for isocratic and gradient separation (<3.5% RSD in retention times). Demonstrated applications include the analysis of triglycerides in different vegetable oil samples. This system is expected to be well suited for generating other types of gradients, such as pH and ionic strength gradients, in electroseparation techniques. © 2001 John Wiley & Sons, Inc. J Micro Sep 13: 351–360, 2001