Protein and peptide separations on high surface area capillaries

A 50 mu m capillary that has been etched with ammonium hydrogen difluoride is evaluated as a separation medium for capillary electrochromatography. Fo r a tryptic digest of transferrin, the etched capillary gave better resolut ion (more peaks in the overall peptide map) and longer retention than separ ations done under identical experimental conditions on an unetched fused-si lica capillary. Resolution on the etched capillary was improved by lowering the voltage from 300 to 267 V/cm. A four-component protein sample also res ulted in longer retention on an echted capillary than on an unetched fused- silica capillary that were both coated with Polybrene. After correction for differences in electroosmotic flow between the two capillaries, the calcul ated electrophoretic mobilities for all four proteins were lower on the etc hed capillary than on the unetched fused-silica capillary. The results of b oth the tryptic digest and protein experiments strongly indicate the presen ce of chromatographic effects on the etched capillary that contribute to th e increased retention and improved resolution with respect to the unetched fused-silica capillary.