Influence of electrolyte composition on the electroosmotic flow and electrophoretic mobility of proteins and peptides

The influence of electrolyte composition on the electroosmotic flow and peptide/protein migration behavior in capillary zone electrophoresis, either with bare fused-silica or polyacrylamide-coated capillaries, has been investigated. The examined electrolyte solutions consist of buffers tailored for controlling the protonic equilibrium over a wide pH range and effective at masking the active adsorption sites of the capillaries for proteins and peptides. Such buffers are composed of the aliphatic oligoamine triethylentetramine (TETA), in combination with either a monoprotic or a polyprotic acid. The drastic variations in the electroosmotic flow and the inhibition of untoward interactions of basic proteins with the capillary wall observed over a wide pH range were associated with the specific adsorption of TETA ions at the interface between the capillary wall and the electrolyte solution. Modifications of the migration behavior of basic proteins and closely related peptides observed using different buffer anions, such as perchlorate, phosphate and citrate, in combination with TETA may be the result of selective interactions of these counter-ions with the analytes.