Theory of Liquid Chromatography

The term liquid-solid chromatography (LSC) covers a range of techniques:

• adsorption chromatography, when the stationary phase is an active solid (e.g. silica, alumina or a polymer) and separation is based on adsorption affinities between the sample molecules and the surface of the active solid

• ion chromatography, which uses an ion exchange medium

• exclusion chromatography using a stationary phase (e.g. a polymer or porous silica) which separates according to molecular size and shape

• affinity chromatography, which utilizes the unique biological specificity of the analyte and ligand interaction with the stationary phase

Liquid chromatography can be carried out within a tube (column chromatography) or on a fiat sheet of material (planar chromatography) such as a sheet of paper (paper chromatography) or a layer of stationary phase coated on to a support, e.g. a glass or plastic sheet (thin-layer chromatography, TLC). In column chromatography, the stationary phase (liquid plus support) can fill the whole inside volume of the tube (packed column) or be concentrated along the inside wall of the tube, leaving an unrestricted path for the mobile phase in the middle of the tube (open tubular or capillary column). The term column will be used in a general sense to apply to both column and planar chromatography.

A significant difference between GC and HPLC is the permeability of columns used. The permeability (k) is a measure of flow resistance:

Permeable columns are the most desirable and typically $ values are & 500 for spherical microparticles.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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