“…Efforts have therefore been made to identify ways to replace polyampholytes with mixtures of simple monoprotic and diprotic buffers. Frey and coworkers have made among the most significant contributions (Frey, ; Frey et al, ; Frey and Strong, ; Kang and Frey, ; Kang et al, ), but others have made important contributions as well (Liu and Anderson, , , ). In addition, although their work did not focus on chromatofocusing, Yang et al (), Tsonev and Hirsh () and Xu and Glatz () have conducted extensive studies mapping the pH and pI dependence of protein behavior in ion‐exchange systems.…”