Chromatographie de partage centrifuge

An innovative liquid-liquid chromatography without solid support

Centrifugal Partition Chromatography (CPC) is a separation method based on the liquid partition of compounds. Due to the centrifugal field force, one phase stays in the rotor (the stationnary phase), the other one is the mobile as in classical chromatography. The compounds migrate through the rotor according to their partition coefficient Kd:

Process for the separation of three compounds with different partition coefficient:

For a better understanding, a FCPC rotor can be compared a succession of funnels. Funnels are lined-up and loaded with half of the volume of the lightest phase of your biphasic system. During the first step, the sample, dissolved in the lightest phase, is added  in the first funnel. In the second step, the heaviest phase (same volume) is added and the funnel shaken. Compounds are separated according to their affinity for both phases (partition coefficient Kd). In the third step, half of the mobile phase is added in the first funnel and the heavy phase is taken and put in the next funnel simultaneously (step 3). All steps are repeated until you recover your three compounds at the outlet (step 4).

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In CPC, different modes can be used. With both liquid phases, it is possible to choose one phase as the stationary phase and the other as mobile phase. As for the other chromatographic methods, normal mode is applied when the stationary phase is more polar than the mobile phase  and inverse mode when the mobile phase is more polar than the stationary phase. We work with descending mode when the mobile phase is the lower phase and ascending mode in the opposite case.

Elution modes: 

With the isocratic and gradient modes, it is possible to add another elution mode, specific to CCC/CPC: the Dual Mode. This mode consists in inversion of mobile and stationnary phases during the same run.                                                                                                  

Step 1:
a,b,c,d,e, are 5 compounds from a mixture. Their affinity to the mobile phase increases from a to e. According to its partition coefficient, each compound migrates at its own speed towards the exit of the rotor.

Step 2:
The compounds a and b have a stronger affinity for the inferior phase. They are retained in the rotor for a longer period of time.Their migration is slower than c,d and e.

Step 3:
The migration of compounds a and b takes time to go through the entire rotor. As both phases are liquid, it is possible to invert the phase via a valve system: the stationary phase becomes the mobile one and vica versa. The compounds a and b are eluted through the rotor head.

Displacement modes:

     1- pH-zone refining

This development mode is used for the purification of compounds whose electric charge depends on pH value. For example, a mixture of free bases is injected in the organic stationary phase with a base stronger than all the compounds to be separated. This stronger base is called the retainer base. The bases are moved along the rotor by pumping through an acidic aqueous solution of the displacer. Pure products are isolated in the effluent as salts. The associated action of the retainer, the displacer and the solvent system increases the separation of the molecules according to their charge and polarity.

     2-Ion pairs displacement

It is based on the principle of the ion pair in which the solubility of an ionic compound evolves following the nature of the counter-ion, the pH and the solvents. These methods could be classified according to the nature of the counter-ion and the charge of the ionic compounds.