High performance liquid chromatography (HPLC) is a separation technique that uses liquid mobile phase to separate the components of a mixture. The sample is first dissolved in a solvent, then forced to flow through a chromatographic column under high pressure. Within the column, the mixture is resolved into its component parts. Individual HPLC columns may use any one of a number of different phases or processes to induce this resolution including normally bonded phase, reversed phase, size exclusion, ion exclusion, and ion exchange.