99 Column chromatography
Column chromatography, like gas chromatography, uses a tube packed with a stationary
phase, but the mobile phase is a liquid instead of a gas (It is sometimes known asliquid
chromatographyor LC). Instead of temperature gradients, a gradient in the composition
of the liquid phase can be used to separate components.
Column chromatography can be performed on larger molecules which may not be readily
introduced into the gas phase. On the other hand, because of the increased viscosity of liq-
uids compared with gases, liquid chromatography can be a more ponderous process.HPLC
(variouslyhigh-pressure liquid chromatographyorhigh-performance liquid chromatography
) speeds the process and improves its selectivity and sensitivity to a significant degree by
forcing the mobile phase through the chromatographic column with high-pressure pumps.