3. Injection

The ideal injection technique combines several features:

• reflect the composition of the sample;

• allow injection of variable volumes. In order to minimize band broadening, the volumes injected must be less than 2% of the total volume of the separation channel, but it is sometimes necessary to increase these volumes to increase detection sensitivity;

• do not disturb the sample for multiple analyses.

Two injection modes are classically used: hydrodynamic injection and electrokinetic injection. Both are generally available on commercial equipment.