**2.2.7 Sample application**

Commercial IPG strips are dehydrated and must be rehydrated to their original gel thickness (0.5 mm) before use. This allows flexibility in applying sample to the strips. There are 3 methods for sample loading: passive in-gel rehydration with sample, active in-gel rehydration with sample, or cup loading of sample after IPG rehydration. Introducing the sample while the strips are rehydrating is the easiest method. In some specific instances, it is best to rehydrate the strips and then apply sample through sample cups while current is applied.
