Nylon-6 capillary-channeled polymer fibers as a stationary phase for the mixed-mode ion exchange/reversed-phase chromatography separation of proteins

Capillary-channeled polymer (C-CP) fibers extruded from nylon-6 are used as the stationary phase for the ion-exchange/reversed-phase mixed-mode chromatographic separation of a three protein mixture. The nylon-6 C-CP fibers are packed collinearly in a 250 x 1.5-mm i.d. column with an interstitial fraction of approximately 0.6. The effects of four displacing salts at three different pHs are studied with regards to protein retention time, peak width, selectivity, and resolution for a synthetic mixture consisting of myoglobin, ribonuclease A, and lysozyme to determine the optimum mobile phase conditions. The net charge model is found to be inadequate in fully explaining the retention behavior, as the proteins are retained by anion and cation-exchange interactions, as well as hydrophobic interactions with the stationary phase. It is found that pH and displacing salt strength had a significant influence on the retention properties and resolution of the proteins.