Page 55 - Tandem Techniques
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Isotachophoresis
Although based on the same principle of electrophoretic migration, isotachophoresis is carried out in a
different way. The sample is placed at the junction between a leading and terminating electrolyte
contained in a capillary tube. The leading electrolyte must have a higher mobility than any of the
sample components and the terminating electrolyte must have a mobility that is less than any of the
sample components. In addition, the leading electrolyte should have a buffering capability at the pH at
which the samples are to be separated. On the application of the electric field, the compound with the
highest mobility, (3), will migrate faster leaving those moving at a slower rate, (1) and (2), behind. This
results initially in a mixed zone being formed before the leading electrolyte and after the terminating
electrolyte. The sample components can never enter the leading electrolyte because their mobility is less
than that of the electrolyte. In a similar manner, the terminating electrolyte can never enter the sample
mixture as its mobility is less than those of the sample components.
Figure 1.10
An Isotachophoresis Separation
