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Tuesday, April 19, 2011

Chromatographic Terms

Column bank A term used in size exclusion chromatographic separations when more than one column is connected in series in
order to generate sufficient molecular weight discrimination.

Column efficiency A measure of the overall performance of a column with respect to peak shape, retentivity, resolution, and speed.
In a very general way, a column is considered more efficient if it generates more theoretical plates, a more symmetric peak and can
resolve many analytes in a short period of time.

Column length, L The distance from the column inlet to its outlet that contains stationary phase.

Column oven In most conventional GC systems the column is housed in a sealed area, the oven, that is heated to produce the tem-
perature gradient. Note that part of the heating and cooling process in a GC separation involves the heat transfer from the heating element
in the oven to the gas around the column and ultimately to the column itself. Therefore, extremely rapid temperature increase rates are not
possible (e.g., a typical temperature gradient falls into the 1–20°C/min range).

Column switching Used to prevent unwanted or column-damaging components in the sample from reaching the separation
column or generate trace enrichment of a component by concentrating the analyte band at the head of a column. The switching system consists of two or more columns and one or more valve placed in series. Flow is directed by switching the valves and redirecting the flow stream.

Chromatogram The detector response vs. time profile that is generated during a separation.

Desalting The process by which simple salts are removed from high-molecular-weight compounds.

Diethylaminoethyl (DEAE) A common substituent used as a weak anion-exchange functional group.

Effluent The entire mobile-phase stream that exits the column.

Elution The process involved in moving an analyte band through or along a support material.

Elution profile
The resulting detector response vs. time output.The elution profile, when reproducible, is used for peak identification,
system performance evaluation, and quantitation. These profiles are typically generated from primary standard compounds, and samples are compared against them.

Elution volume is the volume of eluent required to cause elution

Exclusion limit A parameter used in size-exclusion chromatography that represents the lowest molecular weight that is excluded from
all pores in the packing material.

Fast protein liquid chromatography (FPLC) A low-pressure technique used to separate proteins

Stationary Phase The stationary phase is one of the two phases forming a chromatographic system. It may be a solid, a gel or a liquid. If a liquid, it may be distributed on a solid. This solid may or may not contribute to the separation process. The liquid may also be chemically bonded to the solid (Bonded Phase) or immobilized onto it (Immobilized Phase).

Mobile Phase A fluid which percolates through or along the stationary bed, in a definite direction. It may be a liquid (Liquid Chromatography) or a gas (Gas Chromatography) or a
supercritical fluid (Supercritical-Fluid Chromatography). In gas chromatography the
expression Carrier Gas may be used for the mobile phase. In elution chromatography the
expression Eluent is also used for the mobile phase.

Sample The mixture consisting of a number of components the separation of which is attempted on the chromatographic bed as they are carried or eluted by the mobile phase.

Solvent A term sometimes referring to the liquid stationary phase in partition chromatography.

Illustrated Pocket Dictionary of Chromatography, by Paul C. Sadek.