Highly linear pH gradients for analyzing monoclonal antibody charge heterogeneity in the alkaline range: Validation of the method parameters

• We validated a method for the quantification of antibody charge variants.
• We present different methods for the creation of a suitable standard material.
• The method is valid for charge variants contents of 1% or higher relative abundance.

Cation exchange chromatography has been routinely used for the quantification of monoclonal antibody (mAb) charge heterogeneity. A previously developed method utilizing pH gradients for the elution instead of salt gradients was validated according to current guidelines proposed by the ICH. The linearity, stability, accuracy, precision and the lower limit of quantification have been determined, using pure charge variant standards. The method is valid for the quantification of mAb samples with a charge heterogeneity between 1% and 50%. Three different approaches to obtaining pure standard material for the validation of bio-analytical methods for the quantification of charge heterogeneity of IgG are presented. These methods are based on salt gradient elution, pH gradient elution and displacement in cation exchange chromatography.