A U.S. Patent for “Ionic Strength Mediated pH Gradient Ion Exchange Chromatography” was awarded to Genentech on July 14th, 2020. The present invention is a method for analyzing a composition comprising a polypeptide and one or more charge variants of the polypeptide, the method comprising a) binding the polypeptide and one of more charge variants of the polypeptide to an ion-exchange chromatography material using a loading buffer, wherein the loading buffer is at a first pH and comprises a first ionic strength; b) eluting the polypeptide and one or more charge variants of the polypeptide from the ion-exchange chromatography material using an elution… Learn More