User:Canada Hky/GCMSApps

Gas chromatography (GC), is a common type of chromatography used for separating and analyzing compounds that can be vaporized without decomposition. Typical uses of GC include testing the purity of a particular substance, or separating the different components of a mixture (the relative amounts of such components can also be determined). Mass spectrometry (MS) is an analytical technique for the determination of the elemental composition of a sample or molecule. It is also used for elucidating the chemical structures of molecules, such as peptides and other chemical compounds. The MS principle consists of ionizing chemical compounds to generate charged molecules or molecule fragments and measurement of their mass-to-charge ratios.

Gas chromatography-mass spectrometry combines these two techniques, using the ability of the GC to separate and vaporize the sample and the ability of the MS to provide structural information used to identify compounds. GC-MS has many applications in research, industry and day-to-day life.

Environmental contaminants
Many environmental contaminants are stable at high temperautres, and have low mass, which makes them amenable to analysis using GC-MS. Non-specific detectors such as electron capture and thermal conductivity have been used in the past for this research, but they do not provide the confirmation of identity that is available with GC-MS. Persistent Organic Pollutants (POPs), including pesticides and polychlorinated biphenyls(PCBs) are routinely monitored in environmental samples using GC-MS.

Most environmental monitoring using GC-MS is done with electron ionization (EI). EI offers many advantages, including its robustness, adequate sensitivity and the ability to identify unknowns by comparison to an established library of standards. In an effort to improve detection limits, some researchers are using negative chemical ionization (NCI) for halogenated species, including many pesticides. NCI can lower detection limits and reduce interferences from the sample matrix. Reducing interferences from the sample matrix can reduce sample preparation demands and increase sample throughput. With NCI, it is more difficult to identify unknown species, as there is no commercially available library.

GC-EI-MS has been used for the identification of pesticides in agricultural soil samples, soil samples from residential areas or for the confirmation of identity when other detection methods were used. Pesticides can be found in other environmental matrices, GC-MS has also been used for the identification and quantitation of pesticides in water , sediments and air. Some halogenated pesticides in atmospheric samples have been analyzed using GC-NCI-MS.

Criminal analysis
GC-MS has been used in many legal cases to analyze evidence from a crime scene. Because of the extensive library available with EI, one of the main uses of GC-MS is the identification of unknown substances. These substances are dissolved in a GC suitable solvent or vaporized in order to be introduced into the MS.

Toxicology
GC-MS can also be used in legal cases for toxicological analysis. This can include routine drug tests and the identification of toxins causing death or inebriation (including date rape drugs). Because of the extensive library available with GC-EI-MS, it is an especially valuable tool for the identification of rare and obscure drugs which might not be part of a routine screen.

Law Enforcement
GC-MS is increasingly used for detection of illegal narcotics, and may eventually supplant drug-sniffing dogs.[1] It is also commonly used in forensic toxicology to find drugs and/or poisons in biological specimens of suspects, victims, or the deceased.

Security
A post-September 11 development, explosive detection systems have become a part of all US airports. These systems run on a host of technologies, many of them based on GC-MS. There are only three manufacturers certified by the FAA to provide these systems, one of which is Thermo Detection (formerly Thermedics), which produces the EGIS, a GC-MS-based line of explosives detectors. The other two manufacturers are Barringer Technologies, now owned by Smith's Detection Systems, and Ion Track Instruments, part of General Electric Infrastructure Security Systems.

Food, Beverage and Perfume Analysis
Foods and beverages contain numerous aromatic compounds, some naturally present in the raw materials and some forming during processing. GC-MS is extensively used for the analysis of these compounds which include esters, fatty acids, alcohols, aldehydes, terpenes etc. It is also used to detect and measure contaminants from spoilage or adulteration which may be harmful and which is often controlled by governmental agencies, for example pesticides.

Astrochemistry
Several GC-MS have left earth. Two were brought to Mars by the Viking program. Venera 11 and 12 and Pioneer Venus analysed the atmosphere of Venus with GC-MS. The Huygens probe of the Cassini-Huygens mission landed one GC-MS on Saturn's largest moon, Titan. The material in the comet 67P/Churyumov-Gerasimenko will be analysed by the Rosetta mission with a chiral GC-MS in 2014.

Medicine
In combination with isotopic labeling of metabolic compounds, the GC-MS is used for determining metabolic activity. Most applications are based on the use of 13C as the labeling and the measurement of 13C/12C ratios with an isotope ratio mass spectrometer (IRMS); an MS with a detector designed to measure a few select ions and return values as ratios.