Development and validation of a rapid capillary zone electrophoresis method for determining charge variants of mAb

This work aimed to develop a rapid capillary zone electrophoresis (CZE) method to provide abundant purity and identity information of monoclonal antibodies. The CZE running buffer system was optimized to be 20mM acetate-acetic acid (pH 6.0) together with the co-addition of 0.3% polyethylene oxide (PEO) and 2mM triethylenetetramine (TETA), which was further tested with advantages on the peak resolution improvements. The conditioning period was scheduled to 1 min for both 0.1M HCl and CZE running buffer to reduce total separation time. Additionally, the applied voltage and effective separation length were optimized at 30 kV and 20 cm separately. Compared with the method reported by Yan [1], this newly developed method showed a higher resolution in separating the two unknown basic peaks by testing monoclonal antibody sample (mAb1). The further validation results showed that for all five of charge isoform peaks of test mAb1, repeatability, intraday and interday precision had a RSD less than 0.58% for migration time and less than 3.18% for corrected area percent. The correlation coefficients of more than 0.98 for all peaks also demonstrated the good linearity for the method. In addition to the application of distinguishing intact antibody from C-terminal Lys variants, the method also has advantage in separating the Fab, Fc and intact antibody-relevant substances quickly, which facilitated the rough evaluation of papain induced digestion.