Solvent modulated linear pH gradient elution for the purification of conventional and bispecific antibodies: Modeling and application

•Externally generated linear pH gradients were used for preparative CEX of a conventional and a bispecific antibody.•A model based on simple linear pH gradient elution experiments was used to characterize protein retention.•Rational design of pH step elution procedures is demonstrated without further optimization experiments necessary.•The removal of product-related impurities could be significantly improved using PEG as a mobile phase modulator.