Separation of proteins and peptides by capillary electrochromatography in diol- and octadecyl-modified etched capillaries.

This study involves the evaluation of a capillary electrochromatography method based on etching the inner walls of a fused-silica tube, which is subsequently modified by a silanization/hydrosilation reaction scheme. Two different organic moieties, octadecyl and diol, are attached to the etched capillary wall. The performance of these two columns is compared to a bare capillary using peptide (angiotensins) and protein samples. It is concluded that the etching process increases the surface area of the inner wall sufficiently to induce solute-bonded phase interactions for the capillaries modified with the octadecyl and diol moieties. The separation capabilities of the two modified capillaries are not the same, presumably due to differences in the chemical properties of the two ligands. When compared to a bare capillary where separation is due only to electrophoretic mobility effects, the bonded etched capillaries also exhibit significant differences in separation factors for the same solutes under identical experimental conditions.