A number of novel elution strategies are available when you use a liquid stationary phase. This is because you are now operating a liquid/liquid, rather than a liquid/solid, system in a column. These yield significant performance advantages in terms of separation time, loading constraints (caused by solubility) and productivity compared to the standard elution method. These new possibilities are outlined below:
Standard elution
The stationary phase is retained while the mobile phase flows in one direction only. Either phase can be the mobile one, and therefore you can perform a separation in either normal (organic phase mobile) or reverse (aqueous phase mobile) phase.Elution Extrusion
This strategy makes use of the fact that your compound may be fully separated inside the column before eluting from it. Since you are using a liquid stationary phase, it is possible to recover the separated compound without completing a full elution cycle.
In elution extrusion, you start the separation in the same manner as in standard-mode CCC. However, when your run reaches a certain point you stop the mobile phase and pump in stationary phase to extrude the column contents. This enables your purification cycle and solvent usage to be significantly reduced. After extrusion, the column is completely replenished and ready for your next sample injection.
Dual-mode
When operating a dual-mode elution operating strategy, you first pump the aqueous phase as the mobile phase (I.e. normal phase operation) and after a set period of time you pump the organic phase as the mobile phase (i.e.reverse phase operation). You can repeat this switching procedure a number of times until your desired resolution of purification is achieved. Your advantage of this method is that compounds that have a strong affinity for the original stationary phase can also be separated quickly, rather than waiting a long time for themto elute in the mobile phase.
pH Zone Refining
This elution strategy uses the phenomena that charged entities (ions) prefer the aqueous phases and uncharged molecules prefer organic phases and utilises basic organic phases and acidic aqueous phases (or vice versa) . The analytes dissolved in the stationary phase are eluted by mobile phase according to their pKa values and solubility.
This strategy enables you to achieve very high loading capacity and high resolution separations for those molecules that have the necessary characteristics.
