Retention dependence on weighted average charge

Foley [33] has indicated that for any eluite which can exist in more than one chemical form due to secondary chemical equilibria, retention is given by the summation of the weighted average capacity factors for each eluite form. The mole fraction of each of the eluite species is calculated and used as weighting factors in this treatment. For the trivalent metal ion system described above, M , and 

ML3 coexist in solution, and the capacity factor for the single peak observed is given by  

This equation is concise, but it is often difficult or impossible to isolate the metal species of a dynamic system and preserve their integrity throughout the duration of an experiment designed to determine individual k j values. In our ovra studies, we have examined alternate forms of the retention equation and have found good correlation between predicted and experimental retention times by substituting the charge (Zj) of each metal species for the k terms in eqn. 19. Rewritten in this form, the relative retention for the trivalent metal is  

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