glossary of hplc terms
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Glossary of HPLC Terms
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Activity
In adsorption chromatography, this is the relative strength of the surface of the packing. For silica gel, the
more exposed the silanol groups, the more active the surface. Activity can be controlled by adding water
or another polar modifier, which is hydrogen bonded to the active sites, thereby reducing the surface
activity.
Adsorbent
Packing used in adsorption chromatography. Silica gel and alumina are the most frequently used
adsorbents in HPLC.
Adsorption
The process of interaction between the solute and the surface of an adsorbent. The forces involved can
be strong such as hydrogen bonds, or weak such as van der Waals forces. For silica gel, the silanol group
is the driving force for adsorption, and any solute functional group that can interact with this group can be
retained by liquid-solid chromatography on silica.
Adsorption chromatography
One of the basic LC modes which relies on the adsorption process to effect the separation. Silica gel and
alumina are the most frequently used supports. The molecules are retained by the interaction of their
polar functional groups with the surface functional groups such as silanols of silica.
Adsorption isotherm
In adsorption chromatography, this is a plot of the equilibrium concentration of sample in the mobile
phase per unit volume verses the concentration in the stationary phase per unit weight. The shape of the
adsorption isotherm can determine the chromatographic behavior of the solute such as tailing, fronting,
and sample overload.
Affinity chromatography
A technique in which a biospecific adsorbent is prepared by coupling a specific ligand (such as an
enzyme, antigen, or hormone) for the macromolecule of interest to a solid support (or carrier). This
immobilized ligand will interact only with molecules that can selectively bind to it. Molecules that will not
bind elute unretained. The retained compound can later be released in a purified state. Affinity
chromatography is not a chromatographic technique but selective filtration.
Alumina
An adsorbent sometimes used in adsorption chromatography. Aluminum oxide (AI203) is a porous