**2.2.9 Sample application by cup loading**

Cup loading can be beneficial in the following cases (Cordwell *et al.* 1997, Görg *et al.* 2000):


Because of its relative difficulty and tendency toward artifacts, cup loading should be avoided if possible. When loading the protein sample from a cup, the IPG strips must be rehydrated prior to sample application. The IPG strips can be rehydrated in a variety of ways.

The rehydration tray is recommended although IPG strips are often rehydrated in 1 or 2 ml pipettes that have been sealed at both ends with Para film. Sample volumes of up to 100 μl can be loaded later onto each gel strip using a sample cup.
