The Thermodynamics of Chromatography - Other Thermodynamic Methods that are Used for Studying Chromatographic Systems > Page 56

                          KABb(KA - KB) + KB                                   (28)

 

where (KAB) is the distribution coefficient of a solute between a mixture of solvents (A) and (B) and a stationary phase,
(KA) is the distribution coefficient of a solute between the pure  solvent (A) and a stationary phase,
(KB) is the distribution coefficient of a solute between the pure  solvent (B) and a stationary phase,
and (b) is the volume fraction of solvent (A) in the mixture.

 

The distribution coefficients are referenced to the solvent mixture and not the stationary phase and are thus are the inverse of the distribution coefficients employed in the chromatography elution equation.

  

 

Now the separation ratio (a(1)(2)) of a pair of solutes, both of which are ditributed between two phases (1) and (2),  is defined by,