HPLC separation and analytical techniques rely on understanding and applying the physical and molecular properties of the analytes in question to capitalise on their different afnities for a mobile phase that the analyte is dissolved in and a stationary (or bound) phase that the mobile phase passes over. The analyte partitions between the mobile and stationary phases and passes through the system at a rate determined by the continuing partition. See Chapter 1 for a description of the interactions and forces that are available to the analyst to utilise.