Capillary Ion-Exchange Chromatography with Nanogram Sensitivity for the Analysis of Monoclonal Antibodies J. Rea, B. Freistadt, D. McDonald, J. Wang Genentech, Inc. Purpose To develop a capillary IEC (c-IEC) methodology for the analysis of nanogram amount of monoclonal antibody (mAb) charge variants. Methods Several key modifications were made to a commercially available liquid chromatography system to perform c-IEC for charge variant analysis of mAbs with nanogram sensitivity. Ion-exchange chromatography resins packed in capillary columns (400 µm I.D.) were obtained commercially, and a salt-gradient method was developed to separate the charge variants of the mAbs. Results We demonstrate the applicability of this method for multiple monoclonal antibodies, including antibody fragments, on different columns from different manufacturers. Linearity and precision of the method was demonstrated, with relative standard deviations (RSDs) of less than 10% for relative peak areas for the main peak and the acidic and basic regions. The relative peak areas were comparable between capillary IEC and conventional scale analytical IEC columns. Conclusion These results demonstrate the excellent sensitivity of this multi-product c-IEC method, which can be used for analyzing charge variants in sample-limited applications, such as early stage candidate screening and to support in vivo studies.