Mobile phase

The liquid or gas that flows through a chromatographic system, carrying sample components past a stationary phase. Its composition and flow affect how components separate and elute.

Elution: The removal of substances from a chromatographic system by passage of a mobile phase. The mobile phase carries retained compounds out of the system.
Stationary phase: The chromatographic material that remains fixed while the mobile phase passes through or over it. Separation depends on differing interactions with these two phases.
High-performance liquid chromatography: A liquid chromatographic technique that uses high pressure to drive solvent through a packed column. Its solvents are selected and often blended to control retention and resolution.
Eluotropic series: An ordering of solvents by their elution strength on a specified chromatographic adsorbent. It helps compare candidate mobile-phase solvents by their ability to displace analytes.
Retention time: The time between sample injection and a compound’s detection at a chromatographic outlet. Mobile-phase strength and flow influence when each compound elutes.
Analyte: A chemical component of a sample that is identified or measured by analysis. Analytes partition between the mobile phase and the stationary phase.
Reversed-phase chromatography: Liquid chromatography using a nonpolar stationary phase and a relatively polar mobile phase. Increasing the organic-solvent fraction commonly strengthens elution in this method.
Solvent polarity: A property describing how unevenly electrical charge is distributed within a solvent’s molecules. Polarity influences solvent interactions, but does not alone determine chromatographic strength.
Solvent strength: A measure of a solvent’s ability to move analytes through a chromatographic stationary phase. Changing solvent strength alters how strongly analytes are retained.
Partition coefficient: The equilibrium ratio of a substance’s concentrations between two phases. It describes how an analyte distributes between mobile and stationary phases.

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