Offline Coupling of Hydrophobic Interaction Chromatography–Capillary Zone Electrophoresis for Monitoring Charge‐Based Heterogeneity of Recombinant Monoclonal Antibodies

A holistic understanding of the charge heterogeneity in monoclonal antibodies (mAbs) is paramount for ensuring acceptable product quality. Hence, biotherapeutic manufacturers are expected to thoroughly characterize their products via advanced analytical techniques. Recently, two-dimensional liquid chromatography (2DLC) methods have gained popularity for resolving complex charged species. Capillary electrophoresis (CE) is regarded as a sensitive and faster tool for charged species estimation in biotherapeutics. In this study, we aim to combine the separation power of chromatographic and electrophoretic tools (liquid chromatography [LC]-CE) so as to achieve maximum resolution of mAb charge variants. Hydrophobic interaction chromatography (HIC) has been used as the preferred LC mode with CE for achieving successful separation of both charge and hydrophobic variants for two of the mAbs (trastuzumab and rituximab). The standalone HIC and capillary zone electrophoresis (CZE) methods separated 4 hydrophobic variants and 7 charge variants for each mAb, whereas the 2DLC method separated 10 and 11 variants for mAbs A and B. On the other hand, the HIC-CZE-UV method resolved 29 variants in mAb A and 23 variants in mAb B. The reproducibility of the HIC-CZE-UV method was demonstrated by % change in values of retention time (RT) and peak area as <5% (mAb A), <3% (mAb B), and <12% (for both mAbs), respectively. Thus, the utility of the proposed LC-CE method for characterization of mAb charge variants has been displayed.