Effects of Buffer pH on Electroosmotic Flow Control by an Applied Radial Voltage for Capillary Zone Electrophoresis

Electroosmotic flow has been shown to be controlled via an applied radial voltage. Many factors determine the effectiveness of this control, and one major factor Is buffer pH. In this study the effectiveness of the applied radial voltage for controlling electroosmotic flow while varying buffer pH Is examined. Previously developed theory Is applied and compared to experimental results for a pH range from 1.4 to 6.32. Analysis time Is dramatically reduced by applying a radial voltage for separation of a peptide mixture at pH 1.4. Theory predicts laminar flow profiles under some conditions when applying this technique. However, experimental evidence at pH 6.32 and 1.4 shows no evidence of band broadening from a laminar flow profile. Theoretical and experimental results Indicate the largest range of effective electroosmotic flow control via an applied radial voltage occurs at low ph. Furthermore, a sigmoidal relationship between electroosmotic flow and applied radial voltage Is clearly apparent under these conditions. In contrast, at high buffer pH (>8) the relationship appears to be linear and Is only over a limited range of flow velocities.