Liquid chromatography (LC) is an analytical chromatographic technique that is useful for separating ions or molecules that are dissolved in a
solvent.
If the sample
solution is in
contact with a second solid or
liquid phase, the different solutes will interact with the other phase to differing degrees due to differences in adsorption, ion-exchange,
partitioning , or size. These differences allow the
mixture components to be separated from each other by using these differences to determine the transit time of the solutes through a
column. Instrumentation Simple
liquid chromatography consists of a
column with a fritted bottom that holds a stationary phase in
equilibrium with a
solvent. Typical stationary phases (and their interactions with the solutes) are: solids (adsorption), ionic groups on a resin (ion-exchange), liquids on an
inert solid support (partitioning), and porous
inert particles (size-exclusion). The
mixture to be separated is loaded onto the top of the
column followed by more
solvent. The different components in the sample
mixture pass through the
column at different rates due to differences in their partioning
behavior between the mobile
liquid phase and the stationary phase. The compounds are separated by collecting aliquots of the
column effuent as a
function of time.
Schematic of a simple liquid chromatographic separation
Conventional LC is most commonly used in preparative scale work to purify and isolate some components of a mixture. It is also used in ultratrace separations where small disposable columns are used once and then discarded. Analytical separations of solutions for detection or quantification typically use more sophisticated high-performance liquid chromatography instruments. HPLC instruments use a pump to force the mobile phase through and provide higher resolution and faster analysis time. Top of Page Copyright © 2000 by Brian M. Tissue, all rights reserved.
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