The stacking boundary in capillary electrophoresis

The stacking boundary (SB) in capillary electrophoresis (CE) is elucidated. The SE is different from the electrolyte boundaries; for example, the composition of the SE changes with time while the composition of the electrolyte boundaries ideally does not change with time. All these boundaries originate from an original concentration boundary found between the sample solution and background solution zones before application of voltage. The differences in electrophoretic mobilities cause them to separate from each other, as verified from the enhanced field Vacancy CE experiments and a special experiment. Theoretical and some experimental studies on the fate of analyte zones in vacancy and differential CE are presented. Some equations are derived that provide insight into the behavior of analyte zones in enhanced field vacancy CE. Furthermore, it was found that the composition and especially the conductivity of the sample solution in vacancy and differential CE experiments are crucial in maintaining reproducibility of data and reliability for qualitative and quantitative analysis. (C) 1999 John Wiley & Sons, Inc.