Chromatography comprises a variety of methods for separating chemical mixtures into individual substances for purification or analysis. The separation requires a solid material, called the stationary phase, and an organic liquid solvent or gas, called the mobile phase. A mixture separates into individual constituents based on polarity or attraction to either the stationary phase or mobile phase. Originally, chromatography was used to separate plant pigments, which appeared as bands of color on the stationary phase, giving the technique its name. Chromatography has developed into a number of techniques, including column chromatography, affinity chromatography, thin-layer chromatography (TLC), gas chromatography, and high-performance liquid chromatography (HPLC), among others. Chromatography is used in pharmaceutical, food processing, scientific research, and environmental testing applications.
Common supplies in a chromatography lab include tubular columns specifically designed for each different process. Liquid chromatography columns (LC columns) are typically made of borosilicate glass and can range widely in volume. They may have polyethylene or PTFE (polytetrafluoroethylene) fittings to connect to laboratory apparatus and tubing, and may have porous supports in the base to hold sorbent material, or "column packings," such as silica gel. A column may have a stopcock to help manage the flow of solvent. Gas chromatography columns are made of glass or metal tubing arranged in coils, and are prepared with a layer of liquid or polymer specific to the substance to be tested. HPLC columns are made to withstand high pressure from pumps that move the solvent through the sample. IC columns are used for ion exchange chromatography and are available pre-packed with a resin that is suited to a particular test.
Chromatography paper is commonly made of cellulose, and is available in rolls, sheets, or circles in a variety of dimensions and thicknesses. Solid phase extraction tubes may come pre-packed with an adsorbent. Thin-layer chromatography supplies include developing tanks, sprayers, and plates. Plates are commonly made of aluminum, glass, or plastic. Tanks that contain the plate during the process may be cylindrical or square and made of HDPE (high-density polyethylene) or polypropylene.