Buffering agents and additives for the background electrolyte solutions used for peptide and protein capillary zone electrophoresis

The background electrolyte solution (BGE) has a strong impact on the separation performance of peptides and proteins in all separation techniques governed by electrophoretic principles, due to its considerable influence on the separation mechanism and on the physicochemical properties of both the sample and the inner surface of the separation device, which mostly consists of a fused-silica capillary tube. This review article examines and discusses the effects of composition and pH of BGE on the electrokinetic phenomena taking place at the solid liquid interface within fused-silica capillaries, generating the electroosmotic flow (EOF), and on the separation performance of peptides and proteins in capillary zone electrophoresis (CZE), which is the most used separation mode of capillary electrophoresis for these biopolymers. The paper reviews and discusses literature relevant to explain how pH, ionic strength, conductivity and composition of BGE employed in peptide and protein CZE influence efficiency, selectivity and resolution and other factors affecting the performance of separation, including the electroosmotic flow. Also examined and discussed is the compatibility of BGE composition with the ionization sources employed for the on-line hyphenation of peptides and proteins CZE with mass spectrometry and with the two most popular on-line preconcentration methods field-amplified sample stacking (FASS) and dynamic pH junction.