# The Thermodynamics of Chromatography - Other Thermodynamic Methods that are Used for Studying Chromatographic Systems > Page 59

Thus, substituting for (a) from (32) and (b) from (33) in equation (31),

_{}

Now, if or
when _{}then the separation ratio will be
independent of the composition of the solvent mixture.

Thus, from equation (30) the condition for the independence of the separation ratio from the solvent composition will be when,

or,

or (34)

Expressing equation (34) in thermodynamic terms using the conventional terms for the standard energy.,