Once a plate has been spotted, it is placed into a glass container with a small amount of solvent. This solvent is called the mobile phase. It is important that the height of the solvent is below the height that the compound was spotted on the plate. As the solvent moves up the TLC plate by capillary action, the compound will also move. The compound will be separated into its components based upon each component’s attraction for the stationary phase versus the mobile phase. Components that are attracted to the mobile phase more than they are attracted to the stationary phase will move further up the column. Attractive forces are based on polarity differences. 