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	Gas Chromatography
		Gas chromatography - specifically gas-liquid chromatography - involves a sample being vapourised and injected onto the head of the chromatographic column.
		The choice of carrier gas is often dependant upon the type of detector which is used.
		A non-selective detector responds to all compounds except the carrier gas, a selective detector responds to a range of compounds with a common physical or chemical property and a specific detector responds to a single chemical compound.
	www.shu.ac.uk /schools/sci/chem/tutorials/chrom/gaschrm.htm (940 words)

	Chromatography and Analytical Chemistry
		These days gas chromatography (GC) is one of the primary analytical techniques used in every forensic laboratory.
		The urea-fatty acid complexes were analyzed by gas-liquid chromatography and gas chromatography-mass spectroscopy that revealed the highest EPA concentration of 48% was at 4 C and 4:1 urea/fatty acid ratio.
		Gas Chromatography (GC) is the most widely used method for separating and analyzing a wide variety of organic compounds and gases.
	www.justchromatography.com (1680 words)

	Gas Chromatography
		Gas chromatography is a powerful means of performing qualitative and quantitative measurements of complex mixtures of volatile substances.
		Gas chromatography uses relatively long packed or open tubular capillary columns and is subsequently far more efficient at separation than fractional distillations with short reflux columns.
		Gas chromatography columns normally have 1,000 to 1,000,000 theoretical plates as opposed to fractionating columns which normally operate in the range of 5-100 plates.
	www.chem.usu.edu /~sbialkow/Classes/361/GC/GC.html (1115 words)

	Chromatography - Polyhedron Laboratories, Inc.
		Chromatography consists of passing the specimen (sample), a mixture that includes the analyte, in what is termed the “mobile phase”, frequently in a solvent stream, through what is known as the “stationary phase.” The stationary phase slows down the transit of the components of the specimen.
		Gas Chromatography utilizes a carrier gas, such as helium or nitrogen and a pressurized gas cylinder to carry the sample through the column.
		Gas Chromatography – Mass Spectrometry (GC-MS) is a type of chromatography that combines the features of gas chromatography and mass spectrometry to distinguish and identify various components in a test sample.
	www.polyhedronlab.com /gas.html (635 words)

	Gas Chromatography
		Gas Chromatography was established by Martin and James in 1952.
		Gas Chromatography is widely used for quantitative and qualitative analysis of mixtures of volatile substances.
		Gas Chromatography is useful in the analysis of air pollutants, alcohol in blood and many other fields.
	www.chemforlife.org /teacher/topics/gas_chromatography.htm (299 words)

	Gas Chromatography Mass Spectrometry: How Does It Work?
		The gas chromatography (GC) portion separates the chemical mixture into pulses of pure chemicals and the mass spectrometer (MS) identifies and quantifies the chemicals.
		It is similar to a running race where a group of people begin at the starting line, but as the race proceeds, the runners separate based on their speed.
		The inject port is heated to 300° C to cause the chemicals to become gases.
	www.unsolvedmysteries.oregonstate.edu /GCMS_05.shtml (495 words)

	Gas Chromatography
		Gas chromatography is not used in the introductory organic chemistry lab, but if you are to continue with more advanced laboratory courses, you will most definitely encounter this invaluable analytical tool.
		The gas must be inert, so as not to react with the sample nor the stationary phase.
		Remember from our general overview of chromatography that separation is dependent upon the characteristic equilibrium that exists between the sample in the mobile and stationary phases.
	www.umich.edu /~orgolab/Chroma/gaschroma.html (550 words)

	Gas Chromatography: The Modern Analytical Tool
		In gas-liquid chromatography, it is the interaction between the gaseous sample (the mobile phase) and a standard liquid (the stationary phase), which causes the separation of different molecular constituents.
		The basic components are an inert carrier gas, most commonly helium, nitrogen or hydrogen, a GC column packed or coated with an appropriate stationary phase, an oven that allows for precise temperature control of the column and some type of detector capable of detecting the sample as it exits or elutes from the column.
		Gas-liquid chromatography works because the molecules in the samples are carried along the column in the carrier gas, but partition between the gas phase and the liquid phase.
	www.practicingoilanalysis.com /article_detail.asp?articleid=352&relatedbookgroup=OilAnalysis (1672 words)

	Capilary column gas chromatography
		This is a special page on gas chromatography, with some important practical and theoretical considerations: info on theory, stationary phases, capillary columns, gas detectors, analytical performance and troubleshooting.
		The gas chromatography technique was first carried out in Austria, and the first exploitation of the method was made by Martin and A T James in 1952, when they reported the gas chromatography of organic acids and amines.
		Chromatography is the separation of a mixture of compounds (solutes) into separate components.
	delloyd.50megs.com /moreinfo/gaschrom.html (3571 words)

	Gas Chromatography module
		Gas chromatography is a method for separating substances in a mixture and measuring the relative quantities of substances.
		In this type of chromatography, a sample is rapidly heated and vaporized, and then a stream of gas carries it along a column that contains a stationary phase.
		The sizes of the peaks may be found by calculating the areas under the peaks or by carefully cutting out the peaks and weighing them on an accurate balance.
	www.uwplatt.edu /chemep/chem/chemscape/labdocs/catofp/chromato/gas/gaschrom.htm (500 words)

	Gas Chromatography, Part I
		A GC is used to separate components of a gas or liquid mixture, and provides information as to the composition of the sample being tested.
		In gas chromatography, a typical carrier gas flow of 30ml/min to 40ml/min flow rate must constantly flow through the instrument.
		It is therefore critical that the carrier gas flows at a constant rate and that the supply is uninterrupted.
	www.specgasreport.com /archive/gc1404.htm (1005 words)

	NetLogo Models Library: Gas Chromatography
		(Gas chromatography is one form of chromatography, involving gases.) Chromatography can even be so sensitive as to separate enantiomers (i.e., molecules that differ only by being mirror images of each other!).
		Practically, in gas chromatography molecules are forced to pass through a porous medium, which acts as the sticky surface.
		But gas chromatography can also be used to simply separate gases without a carrier.) Molecules in this model wander randomly downward through the medium.
	ccl.northwestern.edu /netlogo/models/GasChromatography (717 words)

	CHP - Gas Chromatography (Site not responding. Last check: 2007-10-26)
		Gas chromatography is a chromatographic technique that can be used to separate organic compounds that are volatile.
		A gas chromatograph consists of a flowing mobile phase, an injection port, a separation column containing the stationary phase, a detector, and a data recording system.
		The organic compounds are separated due to differences in their partitioning behavior between the mobile gas phase and the stationary phase in the column.
	www.chem.vt.edu /chem-ed/sep/gc/gc.html (209 words)

	GC-MS Background
		Gas chromatography separates the components of a mixture and mass spectroscopy characterizes each of the components individually.
		In general, chromatography is used to separate mixtures of chemicals into individual components.
		In gas chromatography (GC), the mobile phase is an inert gas such as helium.
	www.gmu.edu /departments/SRIF/tutorial/gcd/gc-ms2.htm (1147 words)

	Gas Chromatography
		Because the mobile phase is gas, solubility in the mobile phase is not really a factor, but volatility (vapor pressure) of the components being analyzed is a close equivalent.
		Much of the early work in gas chromatography involved separating hydrocarbon mixtures such as gasoline on columns in which the liquid phase was a silicone oil.
		When the carrier gas contains molecules larger than those of the carrier gas, less heat is removed from the wire; its resistance increases; and the voltage across the wire increases.
	www.dyerlabs.com /chemistry/gas.html (1850 words)

	Gas Chromatography
		In gas chromatography (GC), the stationary phase is a high-boiling liquid and the mobile phase is an inert gas.
		The process of gas chromatography is carried out in a specially designed instrument.
		The carrier gas is an inert gas, helium.
	orgchem.colorado.edu /hndbksupport/GC/GC.html (1222 words)

	Wiley-VCH - Grob, Robert L. / Barry, Eugene F. (eds.) - Modern Practice of Gas Chromatography
		The Fourth Edition of Modern Gas Chromatography represents all of the changes in GC technology that have come about since the publication of the Third Edition.
		Qualitative and Quantitative Analysis by Gas Chromatography (Robert L. Grob and Mary A. Kaiser).
		Physicochemical Measurements by Gas Chromatography (Mary A. Kaiser and Cecil R. Dybowski).
	www.wiley-vch.de /publish/dt/books/bySubjectCH00/bySubSubjectCH11/0-471-22983-0/?sID=399c93ef890358f8f88a7b73d32006c7 (334 words)

	Practical Gas Chromatography.
		This technique was first carried out in Austria, and the first exploitation of the method was made by Martin and A T James in 1952, when they reported the gas chromatography of organic acids and amines.
		Chromatography (2) is the separation of a mixture of compounds (solutes) into separate components.
		The type of detector gas is dependent on the specific detector and is fairly universal between GC manufacturers.
	delloyd.50megs.com /whats_new.html (4306 words)

	R.M. R. Gas Chromatography
		The common practice is to use an inert carrier gas such as helium to sweep the sample we wish to separate through the column and to detect the components as they emerge from the far end.
		When gas particles, atoms or molecules, approach a solid surface there is, except in some special circumstances, a repulsive force which causes the particle to come to rest, reverse course, and re-enter the gas phase.
		Gas chromatographs have also been used in conjunction with a mass spectrometer whereby the emerging components from the GC column are passed over a permeable membrane at the input of the mass spectrometer.
	www.smecc.org /gas_chromatography.htm (3493 words)

	Gas Chromatography
		Chromatography in which the stationary phase (often water) is more polar than the mobile phase.
		In ‘headspace chromatography’ the vapor phase is analyzed as an indication of concentration in the liquid phase.
		Generally, any chromatography in which the mobile phase is a liquid; but sometimes used to mean column chromatography at little or no applied pressure.
	www.dyerlabs.com /chemistry/glossary.html (1101 words)

	Sourcing Hydrogen for Gas Chromatography
		Gas Hydrogen supply is initiated from one side of the switchover system, and is automatically switcheds to the other side as the primary source is depleted.
		Because of the proximity of the gas source to the GC, delivery pressure monitoring and adjustment are easily accomplished in using this arrangement.
		Contaminant levels for a given grade of hydrogen may vary from cylinder to cylinder, and still meet specification, as long as the total level in each cylinder is. This cylinder-to-cylinder variation may be a consideration for sensitive analyses, as it introduces another variable into the operation.
	www.coleparmer.com /techinfo/techinfo.asp?htmlfile=sourcing-hydrogen.htm&ID=711 (1478 words)

	Gas Chromatography
		In general, chromatography is a term that describes techniques used to separate components of mixtures.
		In gas chromatography, a gas is used to carry a mixture across a bed of material.
		Gas chromatography is a widely used technique that has been applied to a plethora of complex mixtures across a diverse sampling of disciplines
	faculty.kutztown.edu /betts/html/GC.htm (669 words)

	EPA - Air - OAQPS - APTI - Air Pollution Control - Gas chromatography
		Gas chromatography (GC) coupled with a flame ionization detector (FID) is employed for qualitative identification and quantitative determination of volatile organic compounds (VOCs) in air pollution monitoring.
		The gas chromatograph, or GC, consists of a column, oven and detector.
		In the gas chromatograph, a sample goes to the column, separates into individual compounds and proceeds through the hydrogen flame ionization detector.
	www.epa.gov /air/oaqps/eog/course422/ce4b3.html (255 words)

	BISC 429
		Gas chromatography is a very sensitive method for the separation and quantification of chemicals, and it is perfect for the analysis of fatty acid components.
		In gas chromatography, the mobile phase is a gas that is moved through the column, while the stationary phase is a liquid film that coats the column filling (in packed columns) or the column wall (in capillary columns).
		Compounds must be present in the gas phase so that partition between the gaseous mobile phase and the liquid stationary phase is possible.
	www.sfu.ca /bisc/bisc-429/GLC.html (2762 words)

	Contaminant analysis techniques
		Gas chromatography is one of the most widely used methods to determine the chemical make-up of a complex, volatile mixture.
		Before gas chromatography can be performed, the sample must be disolved in a volatile solvent like iso-octane.
		In many of the pioneering studies which used gas chromatography, columns were 2 to 3 metres long, with a diameter of 2 to 4 mm, and made of glass or metal.
	whale.wheelock.edu /bwcontaminants/analysis.html (1464 words)

	Biotech Bunny: Gas Chromatography
		Gas chromatography makes use of a pressurized gas cylinder and a carrier gas, such as helium, to carry the solute through the column.
		There are three types of gas chromatography that will be discussed here: gas adsorption, gas-liquid and capillary gas chromatography.
		Gas adsorption chromatography involves a packed bed comprised of an adsorbent used as the stationary phase.
	www.rpi.edu /dept/chem-eng/Biotech-Environ/CHROMO/chromgas.html (219 words)

	Gas Chromatography Theory
		Gas Chromatography (GC) is a commonly used analytic technique in many research and industrial laboratories.
		The mobile phase (=carrier gas) is comprised of an inert gas e.g.
		It is based on the comparison of two gas streams, one containing only the carrier gas, the other one the carrier gas and the compound.
	www.chem.ucla.edu /~bacher/General/30BL/gc/theory.html (743 words)

	D3054-98 Standard Test Methods for Analysis of Cyclohexane by Gas Chromatography (Withdrawn 2007)
		These test methods cover the determination of the hydrocarbon impurities typically found in cyclohexane and the purity of cyclohexane by difference by gas chromatography.
		These test methods are applicable to impurity concentrations in the range of 0.0001 to 0.1000 wt% and for cyclohexane purities of 98 % or higher when using the internal standard procedure.
		Formerly under the jurisdiction of Committee D16 on Aromatic Hydrocarbons and Related Chemicals, these test methods were withdrawn in February 2007 in accordance with section 10.5.3.1 of the Regulations Governing ASTM Technical Committees, which requires that standards shall be updated by the end of the eighth year since the last approval date.
	www.astm.org /DATABASE.CART/REDLINE_PAGES/D3054.htm (295 words)

	Gas Chromatography Advantages (Site not responding. Last check: 2007-10-26)
		The major advantage of gas chromatography is the very high resolving (i.e.,separating) power provided by the capillary columns that are typically used.
		Because the mobile phase is in a gas, the gas chromatograph can be readily interfaced to a mass spectrometer.
		Finally, gas chromatography can used for the analysis of many classes of organic contaminants.
	www.uga.edu /srel/AACES/GCtutorial/page6.html (175 words)

	Advisory Opinion: Gas Chromatography Field Analysis
		The purpose of this Advisory Opinion is to raise awareness of field portable gas chromatography (GC) technology and its on-site application in the Northeast.
		Gas chromatography is a separation technology, not an analytical technology in itself.
		Gas chromatography is used to separate a mixture of closely-related compounds into the individual compounds for measurement.
	www.newmoa.org /Newmoa/htdocs/cleanup/advisory/gc.htm (4848 words)

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