Department of Chemistry
Stage 2 Chemistry Social Relevance
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Chromatography is a separations
method that relies on differences in partitioning
behavior between a flowing mobile phase and a stationary phase
to separate the the components in a mixture.
A column (or other support for TLC, see below) holds the stationary
phase and the mobile phase carries the sample through it. Sample
components that partition strongly into the stationary phase spend
a greater amount of time in the column and are separated from
components that stay predominantly in the mobile phase and pass
through the column faster.
As the components elute from the column they can be quantified
by a detector and/or collected for further analysis. An analytical
instrument can be combined with a separation method for on-line
analysis. Examples of such "hyphenated techniques" include
gas and liquid chromatography with mass spectrometry (GC-MS and
LC-MS), Fourier-transform infrared spectroscopy (GC-FTIR), and
diode-array UV-VIS absorption spectroscopy (HPLC-UV-VIS).
Specific chromatographic methods:
- Gas chromatography (GC)
- Applied to volatile organic compounds. The mobile phase is
a gas and the stationary phase is usually a liquid on a solid
support or sometimes a solid adsorbent.
- High-performance liquid chromatography
- A variation of liquid chromatography that utilizes high-pressure
pumps to increase the efficiency of the separation.
- Liquid chromatography (LC)
- Used to separate analytes in solution including metal ions
and organic compounds. The mobile phase is a solvent and the
stationary phase is a liquid on a solid support, a solid, or
an ion-exchange resin.
- Size-exclusion chromatography (SEC)
- Also called gel-permeation chromatography (GPC), the mobile
phase is a solvent and the stationary phase is a packing of porous
- Thin-layer chromatography (TLC)
- A simple and rapid method to monitor the extent of a reaction
or to check the purity of organic compounds. The mobile phase
is a solvent and the stationary phase is a solid adsorbent on
a flat support.