Preparative Column Isotachophoresis

 

A diagram of two preparative column systems are shown in figure 21, the left hand side diagram representing the normal isotachophoresis system the other employing ampholytes to improve the separation. The function of ampholytes has already been briefly considered but the subject now needs some further discussion.

 

                     Normal Isotachophoresis                         Isotachophoresis Employing

                                                                                                 Ampholyre Spacers

 

Figure 21. Normal Isotachophoresis and Isothachophoresis Employing Ampholytes

 

As dealt with earlier, ampholytes are molecules that contain both acid and basic groups and, thus, can become cations or anions depending on the pH of the medium in which they are dissolved.. The pH at which the molecule becomes uncharged is known as the isoelectric point and the uncharged or neutral molecule is then called a zwitter ion. The zwitter ion is almost always polar and as a consequence, very water-soluble. The samples are collected by an appropriate flow system after separation and the individual components being separated by ampholytes are completly free from each other and only need be separated from their adjacent ampholytes.  The presence of ampholytes also reduces the precision necessary for sampling each sample band as slight late, or early sampling only affects the amount of ampholyte present in the collected fraction