# The Thermodynamics of Chromatography - Other Thermodynamic Methods that are Used for Studying Chromatographic Systems > Optimum Operating Conditions for Chiral Separations in Liquid Chromatography > The Effect of Temperature and Solvent Composition on the Required Column Efficiency > Page

### The Effect of Temperature and Solvent Composition on the Required Column Efficiency

Using the values for the capacity ratios and separation ratios derived from equations (47), (48) and (49) in equation (39) the efficiency necessary to ensure a separation of (6s) for the two enantiomers can be calculated over a range of temperatures and solvent compositions.

**Figure 22.
Graphs of Required Efficiency against Temperature for Each Solvent Composition**

Curves
relating required efficiency against temperature for each solvent composition,
calculated in this manner, are shown in figure 22. As would be expected, the
minimum efficiency is required at the lowest temperature and lowest ethanol
concentration. As either the separation ratio and/or the capacity ratios
decrease, the necessary efficiency to achieve a separation increases (as
predicted by equation (39)). At one extreme, where the capacity ratio is very
small (*i.e.* at 50% v/v ethanol and 50˚C), 15000 theoretical plates
is necessary for separation. However, if the volume fraction of ethanol is set
at 0.05, then even at 50˚C, separation is achieved with less than 3000 theoretical
plates.