The mobile phase refers to the solvent that is used to separate components in a liquid sample for analysis in high performance liquid chromatography (HPLC). HPLC is a technique used for the separation, identification, and quantification of every individual component in a mixture.

During the process, the pressurized mobile phase or liquid solvent containing the sample mixture is passed through a column filled with a solid adsorbent material. The different components in the sample interact with the adsorbent material slightly differently. This results in different flow rates for each component causing each one to flow out of the column separately. As each component flows out of the column, it is collected, identified, and quantified.