Elimination of light chain tailing in reducing capillary electrophoresis with sodium dodecyl sulfate analysis of a monoclonal antibody

Capillary electrophoresis with sodium dodecyl sulfate (CE‐SDS) is a common analytical technique for investigating the purity and molecular size heterogeneity of monoclonal antibody (mAb) drugs. In reducing CE‐SDS analysis of mAb‐A, the light chain (LC) peak exhibited severe tailing, seriously affecting the purity analysis. The purposes of this investigation are to clarify the source of tailing and develop a more appropriate CE‐SDS method to eliminate LC tailing. The degree of LC tailing was closely related to the mAb concentration, SDS concentration, and injection amount, and more hydrophobic detergents, such as sodium hexadecyl sulfate (SHS) and sodium tetradecyl sulfate (STS), could be used instead of SDS to obtain better peak shapes. The results also indicated that the tailing was caused by the binding problem associated with SDS, and SHS/STS could provide a more stable and uniform complexation for the LC. In summary, the method we developed successfully eliminated the LC tailing and provided a robust characterization of mAb‐A in reducing CE‐SDS analysis.