Liquid Chromatography

Liquid chromatography is a collection of separation and purification techniques.  A sample mixture of analytes injected into a liquid solvent is passed through a stationary phase (typically a column packed with porous particles).  As a mixture moves through the column, each individual component interacts uniquely with the stationary phase, and shows a particular affinity toward the materials it is moving past.  Subtle differences in affinity each analyte shows toward the packing material sets up a differential migration for the various components. Analytes group up into elution "bands" and exit the column, past the detector with signature retention times. 

In the setting of analysis and purification, target analytes interact with stationary phase media under the influence of a wide array of factors.  Hydrophobic and electrostatic interactions, as well as hydrogen bonding and protein conformation all control the movement of analytes through the chromatographic system.  Subtitle changes in one or more of these factors either drive analytes to bind to the stationary phase or disrupt this connection causing them to elute.  A carefully orchestrated system of "catch and release", or bind and elute is performed in LC to control the position of molecules moving through a mixture.

There are several different types of liquid chromatography, including:

• Reversed-phase: Separates analytes based on their hydrophobic/hydrophillic character.

• Ion exchange: Separates analytes based on electric charge. 

• Size exclusion: Separates analytes based on size or molecular weight. 

• Affinity: Separates analytes based on their shape or conformation, and their ability to dock to a targeted receptor ligand. 

Liquid chromatography is widely used to identify, quantify, and collect small and large molecules. It is a key tool in the pharmaceutical, food, forensic science and environmental industries.