Zone Electrophoresis

 

The separation of a four-component mixture by zone electrophoresis is depicted diagrammatically in figure 1. The basic system consists of a tube connecting two reservoirs containing a buffer solution consisting of anions (Q) and cations (P) called the ‘back electrolyte’. In one reservoir is placed an electrode held at a positive potential the anode and the other an electrode held at a negative potential the cathode. The back electrolyte ions (Q) and (P) are at a high concentration and the sample to be separated, containing four components (anions A, B, C and cation D) are present at a significantly lower concentrations are introduced into the centre of the tube. On applying the electric field the anions migrate towards the anode and the cations migrate towards the cathode at speeds relative to their ionic mobilities. Unfortunately, as a result of diffusion the peaks tend to spread and become broader; the faster moving ions disperse to a greater extent than the slower moving ions. This effect is shown in figure 1.

 

 

Figure 1. The Separation of Components A, B, C and D by Zone Electrophoresis

 

As seen from figure 1, all the ionic species are separated and their migration distances are l_A,  l_B, l_C and l_D respectively.

 

Thee R_F values for each anionic species relative to ion C will be,

 

R_F(A) = l_A/ l_C    and      R_F(A) = l_A/ l_C

 

This electrophoretic separation technique is analogous to separations obtained by elution chromatography.