Allowance for "analyte valence" in the retention model of ion-exchange chromatography. Studies of adenosine 5'-phosphates on DEAE cellulose.

Quantitative expressions are derived for various retention models of the ion-exchange behaviour of multivalent analytes. Their effectiveness as descriptions of experimental results is then tested by application to partition equilibrium studies of the effect of phosphate concentration on the interaction between the three adenosine 5'-phosphates and diethylaminoethylcellulose at pH 4.4. A completely general multi-state model has pointed to quantitative deficiencies in the currently accepted cooperative two-state model, which is, however, superior to a multi-state model devoid of cooperative effects. A similar situation pertains to the ion-exchange behaviour of cytochrome c on carboxymethylcellulose at pH 7.0.