Free solution capillary electrophoresis of basic proteins in uncoated fused silica capillary tubing

Abstract

Abstract A series of buffer systems encompassing the pH range from 3.5 to 9.0 have been developed for free solution capillary electrophoretic (CE) analysis of basic proteins in uncoated fused silica capillaries. Separations of model proteins possessing isolectric points between 9.1–11.0 have been achieved with efficiencies in the range of 95,000–690,000 theoretical plates. In each case the modifier 1,3‐diaminopropane is incorporated in the operating buffers at concentrations of 30–60 mM along with moderate levels of alkali metal salts to suppress protein‐capillary wall interactions normally encountered with basic proteins. The combination of these buffer additives allows the analyses to be conducted at pHs below the protein isoelectric points. No special capillary pretreatment is required. The advantages of this approach to analyzing basic proteins include its simplicity, the ability to perform the analyses in the pH range where proteins are stable and the greater flexibility available in the choice of pH as a means of affecting selectivity changes.