Question

What is the principle of micellar electrokinetic capillary chromatography? How does it differ from CZE?

Short answer

The micellar electrokinetic capillary chromatography or MEKC involves the differential movement of micelles that are ionic through the buffer solution. It is different from CZE wherein the surfactant is added such that micelles are formed that form two phases and are negatively charged and move towards the cathode.

Step-by-step solution

Step 1. Given information

Explain the principle of micellar electrokinetic capillary chromatography and its difference from capillary zone electrophoresis (CZE).

Step 2. Principle of micellar electrokinetic capillary chromatography  

Micellar Electrokinetic Capillary Chromatography (MEKC) is a technique that involves the use of a surfactant that has a long chain. It could be sodium dodecyl sulfate. As this has a long hydrocarbon chain, it is identified by a hydrophobic end that has a functional group as its head. The negative charge ends group together to form micelles that move towards the cathode. Besides, in this method both the phases are mobile.

Step 3. Capillary Zone Electrophoresis 

Capillary Zone Electrophoresis (CZE) is one of the simplest forms of capillary electrophoresis. Here the capillary tube is filled with buffer solution and the ends are placed in the solution having additional buffer solution. The end having the sample is considered as anode wherein solutes migrate towards the cathode. The order it elutes is cations first, neutral ions, and then lastly the anions.

The direction of electroosmotic flow can be reversed by adding alkyl ammonium salt wherein the alkyl ammonium ion is hydrophobic and is positively charged and binds with negatively charged silanate ions. The result is positively charged which attracts anions. Here the order of elution is opposite to the normal. CZE helps in separating charged species namely proteins, amines, etc.

Step 4. The main difference between MECC and CZE

1. Micelles are not present in CZE while it is present in MEKC
2. In CZE, the ions migrate according to ionic mobility to separate into zones under influence of the electric field.
3. In MEKC, there is the option of changing column packing to alter the stationary state, unlike CZE.
4. In CZE, it has limitations in separating neutral species.