Peptide purity and counter ion determination of bradykinin by high-performance liquid chromatography and capillary electrophoresis

Abstract

Abstract Bradykinin is a nonapeptide hormone of physiological importance. This peptide can be synthesized in yields as high as 83% by solid-phase synthesis. The work presented in this paper describes peptide purity determination of synthetic bradykinin acetate by both reversed-phase HPLC and CE. For purity determination by HPLC, two types of reversed-phase columns were used with gradient elution. The solvent system consisted of trifluoroacetic acid as the ion-pairing reagent and acetonitrile as the organic modifier. An LPA coated capillary and phosphate–phosphoric acid electrolytes of varied pH values were employed to determine purity by CE. The results obtained from these experiments demonstrated the high resolving power of CE in comparison to HPLC for peptide analysis. In CE, resolution of bradykinin and its impurities was greatly improved by varying the electrolyte pH. CE was also used to determine the content of acetic acid in the bradykinin sample. This was performed using a fused-silica capillary and a buffer consisting of sodium phthalate as the UV-absorbing background electrolyte and cetyltrimethylammonium bromide as the electroosmotic flow modifier under an indirect UV detection mode.