gas chromatography


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chromatography

 [kro″mah-tog´rah-fe]
a technique for analysis of chemical substances. The term chromatography literally means color writing, and denotes a method by which the substance to be analyzed is poured into a vertical glass tube containing an adsorbent, the various components of the substance moving through the adsorbent at different rates of speed, according to their degree of attraction to it, and producing bands of color at different levels of the adsorption column. The term has been extended to include other methods utilizing the same principle, although no colors are produced in the column. adj., adj chromatograph´ic.

The mobile phase of chromatography refers to the fluid that carries the mixture of substances in the sample through the adsorptive material. The stationary or adsorbent phase refers to the solid material that takes up the particles of the substance passing through it. Kaolin, alumina, silica, and activated charcoal have been used as adsorbing substances or stationary phases.

Classification of chromatographic techniques tends to be confusing because it may be based on the type of stationary phase, the nature of the adsorptive force, the nature of the mobile phase, or the method by which the mobile phase is introduced.

The technique is a valuable tool for the research biochemist and is readily adaptable to investigations conducted in the clinical laboratory. For example, chromatography is used to detect and identify in body fluids certain sugars and amino acids associated with inborn errors of metabolism.
adsorption chromatography that in which the stationary phase is an adsorbent.
affinity chromatography that based on a highly specific biologic interaction such as that between antigen and antibody, enzyme and substrate, or receptor and ligand. Any of these substances, covalently linked to an insoluble support or immobilized in a gel, may serve as the sorbent allowing the interacting substance to be isolated from relatively impure samples; often a 1000-fold purification can be achieved in one step.
column chromatography the technique in which the various solutes of a solution are allowed to travel down a column, the individual components being adsorbed by the stationary phase. The most strongly adsorbed component will remain near the top of the column; the other components will pass to positions farther and farther down the column according to their affinity for the adsorbent. If the individual components are naturally colored, they will form a series of colored bands or zones.

Column chromatography has been employed to separate vitamins, steroids, hormones, and alkaloids and to determine the amounts of these substances in samples of body fluids.
exclusion chromatography that in which the stationary phase is a gel having a closely controlled pore size. Molecules are separated based on molecular size and shape, smaller molecules being temporarily retained in the pores.
gas chromatography a type of automated chromatography in which the mobile phase is an inert gas. Volatile components of the sample are separated in the column and measured by a detector. The method has been applied in the clinical laboratory to separate and quantify steroids, barbiturates, and lipids.
gas-liquid chromatography gas chromatography in which the substances to be separated are moved by an inert gas along a tube filled with a finely divided inert solid coated with a nonvolatile oil; each component migrates at a rate determined by its solubility in oil and its vapor pressure.
gel-filtration chromatography (gel-permeation chromatography) exclusion chromatography.
ion exchange chromatography that utilizing ion exchange resins, to which are coupled either cations or anions that will exchange with other cations or anions in the material passed through their meshwork.
molecular sieve chromatography exclusion chromatography.
paper chromatography a form of chromatography in which a sheet of blotting paper, usually filter paper, is substituted for the adsorption column. After separation of the components as a consequence of their differential migratory velocities, they are stained to make the chromatogram visible. In the clinical laboratory, paper chromatography is employed to detect and identify sugars and amino acids.
partition chromatography a process of separation of solutes utilizing the partition of the solutes between two liquid phases, namely the original solvent and the film of solvent on the adsorption column.
thin-layer chromatography that in which the stationary phase is a thin layer of an adsorbent such as silica gel coated on a flat plate. It is otherwise similar to paper chromatography.

gas chro·ma·tog·ra·phy

a chromatographic procedure in which the mobile phase is a mixture of gases or vapors, which are separated in the process by their differential adsorption on a stationary phase.

gas chro·ma·tog·ra·phy

(gas krō'mă-tog'ră-fē)
A chromatographic procedure in which the mobile phase is a mixture of gases or vapors, which are separated by their differential adsorption on a stationary phase.
References in periodicals archive ?
The gas chromatography (GC) market is broadly divided into three major types such as accessories & consumables, instruments, and reagents.
Schantz is the team leader of the Gas Chromatography Team, and S.
Also thermodynamic parameters of polymers were investigated by inverse gas chromatography (IGC), which is a widely used and accepted method for determining physicochemical properties [14, 15] of non-volatile materials such as polymers [16], liquid crystals [17], organic pollutants [18], pharmaceutical products [19, 20], and vegetable oils [21, 22].
Gas chromatography is a standard analytical technique for separating chemicals in a complex sample.
However, at the 228th American Chemical Society meeting held in Philadelphia in August 2004, Pedersen further reported that gas chromatography confirmed all 13 compounds to have been eliminated at two pilot plants testing reverse osmosis for contaminant removal.
Chandler Engineering[TM] offers Carle Gas Chromatography, providing fast and accurate testing of samples with a large selection of pre tested applications.
Presenting the most recent methods in flavour, off-flavour, odour, and malodour analysis, this reference provides the latest advances in mass spectrometry, sample preparation, gas chromatography (GC)-olfactometry, and electronic-nose technology for food, cosmetic and pharmaceutical applications.
Traditional methods for analyzing taints in foods include instrumental headspace gas chromatography, headspace gas chromatography-mass spectrometry, gas chromatography-sniffing systems and human sensory evalution.
This study describes methods for analysis of acetone soluble wood extractives using a combination of high-resolution and low-resolution gas chromatography (GC).
The vapor, now rich in the volatile components of the sample, is extracted and analyzed using gas chromatography. The process of headspace extraction is also referred to as vapor-phase analysis or analysis of equilibrium vapor.
Contract notice: high resolution gas chromatography mass spectrometry (gc-hrms) system

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