Chromatography Techniques

Major Chromatographic Techniques

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Chromatography basically is a method of separation of compounds from a mixture. The technique is both analytical and preparative and is employed widely in industries as well as in laboratories. Chemical analysis is mostly done all over the world with chromatography or any other various techniques related to chromatography. Chromatography is a physical technique and has a vast application in chemical field starting from basic analytical chemistry to forensic science.

Some major chromatography techniques are:

Column chromatography is a method used to purify individual chemical compounds from mixtures of compounds. It is has preparative applications on scales ranging from small scale to large scale production. Relatively low cost and disposability of the stationary phase are the main advantages of column chromatography.

Paper chromatography involves placing a small dot or line of sample solution onto a strip of polar cellulose chromatography paper. The paper is placed in a glass chamber with a shallow layer of solvent and is sealed. As the solvent moves through the paper, it comes in contact with the sample mixture, which starts to rise up the paper with the solvent.

Thin layer chromatography (TLC) is a mostly used technique which involves a stationary phase of a thin layer of adsorbent like alumina, silica gel, or cellulose on a flat, inert layer of substrate. Advantages of TLC are better separations, faster runs, and the choice of different adsorbents. Better quantification and resolution can be achieved with high-performance TLC.

Displacement chromatography is a preparative technique in which a sample is placed onto the head of the column and is then displaced by a solute that is more strongly adsorbed than the components of the original mixture. As a result the components are resolved into consecutive rectangular zones of highly concentrated pure substances rather than solvent-separated peaks.

Gas chromatography (GC) is commonly used in analytical chemistry for separating and analysing compounds that can be vaporized without decomposition. In this process, the mobile phase (or "moving phase") is a carrier gas; commonly an inert gas such as helium or an unreactive gas such as nitrogen is generally used. Stationary phase is a microscopic layer of liquid or polymer on an inert solid support, within a glass or metal tubing.

Supercritical fluid chromatography (SFC) –in this technique the mobile phase is a fluid above and relatively close to its critical temperature and pressure. SFC mainly utilizes carbon dioxide as the mobile phase; in order to pressurize the chromatographic flow. Supercritical phase represents a state in which liquid and gas properties combine.

Expanded Bed Adsorption (EBA) Chromatographic Separation is used for target protein from a raw feed stream when it passes through a chromatography column system containing adsorbent beads. Using this technique the unprocessed raw compound can be treated directly in the chromatographic column, avoiding clarification and pre-treatment steps.