Genetic Analysis - Electroosmotic Flow

Electroosmotic flow (EOF) is a consequence of the surface charge on the capillary wall. Bare fused silica capillaries have ionizable silanol groups in contact with the separation buffer. As the pH of fused silica is about 1.5, any pH above this will generate measurable EOF. Although EOF may be desirable for mixed analyte separations, for DNA sequencing it works to degrade resolution and the reproducibility of migration time. For this reason it is essential to substantially reduce or eliminate EOF in order to effectively improve separation performance.

Figure 1 illustrates the charged silanol groups which produce electroosmotic flow in bare-fused silica capillaries.