# The Thermodynamics of Chromatography - Other Thermodynamic Methods that are Used for Studying Chromatographic Systems > Optimum Operating Conditions for Chiral Separations in Liquid Chromatography > Page 63

and the
capacity ratio (k'_{a)} will be given by,

(37)

For two
enantiomers (a) and (b), enantiomer (b) being the last eluted peak, the
separation ratio (a_{ba}) is given by,

(38)

The efficiency
(n), required to achieve a separation (*i.e*. the solutes are separated by
(6s) is given by the Purnell equation
(14) (see book 6 of this series)

(39)

where (k_{a}) is the capacity ratio of the first
eluted peak and (a_{ba}) is the separation ratio or the two
peaks (*i.e*. a_{ba} = k'_{b}/k'_{a}).