GC-MS gas chromatography and

GC/MS. gas chromatography and mass spectrometry used as a combined technique... 

GC/MS Gas chromatography and mass spectrometry. The most accurate analytical method for testing urine samples and for doing substance analysis. GC/MS is the superior method for analysis of steroids and urine because it detects extremely low levels of steroids and can differentiate one compound from another. A gas chromatograph (GC) isolates each individual component of a substance for analysis by the mass spectrometer (MS). 

Figure 1.2 Overview of the EPA s organics protocol. VOCs, volatile organics SVOCs, semivolatile organics OCs/PCBs, organochlorine pesticides/poly-chlorinated biphenyls HS-GC-FID, static headspace coupled to gas chromatography and flame ionization detection LLE, liquid-liquid extraction LSE, liquid-solvent extraction or solvent leaching from solid matrices GC-ECD, gas chromatography and electron-capture detection GC-MS, gas chromatography and mass spectrometry RP-SPE, reversed-phase solid-phase extraction.

Several analytical tools coupled to mass spectrometers as GC-MS (gas chromatography) and LC-MS (liquid chromatography), including ICP-MS (inductively coupled argon plasma), SCF-MS (supercritical fluid), NMR-MS (nuclear magnetic resonance), and IR-MS (infrared-MS), are routinely used to determine the phenolic acids. With the development of soft ionization techniques, fast atom bombardment (FAB) [19] and plasma desorption (PD) [20], followed by the electrospray ionization (ESI) [21], have been used for phenolic acid analyses. 

Scientists need to classify and organize complex data, such as that yielded by medical tests or analysis via GC-MS (gas chromatography-mass spectrometry). The data may be multifaceted and difficult to interpret, as different tests may conflict or yield inconclusive results. Growing cell structures may be used to assess medical data for example, such as that obtained from patient biopsies, and determine whether the test results are consistent with a diagnosis of breast cancer.1... 

Chromatographic methods are also often used as part of systems that are called hyphenated methods, (see Chapter 15) where the output of the chromatographic section is used as the input for an identification method such as mass spectrometry. These hyphenated methods are also most often referred to by their acronyms, for example, GC-MS—gas chromatography-mass spectrometry and HPLC-MS—high-performance liquid chromatography-mass spectrometry. Note that although ultraviolet-visible (UV-Vis) is hyphenated, it is not a hyphenated method in that it does not consist of two different methods of analysis. Hyphenated methods will be discussed fully in Chapter 15. 

Mass spectrometry (MS) is probably a famhiar tool to chemistry and biology students as a technique commonly used to measure the molecular mass of a sample. Often, MS is used in tandem with other techniques for chromatic separation of the sample before mass measurement. Some common hyphenated techniques include HPLC-MS, high-pressure liquid chromatography coupled to MS GC-MS, gas chromatography coupled to MS or CE-MS, capillary electrophoresis coupled to MS. 

Lucas SV. 1984. GC/MS (gas chromatography-mass spectrometry) analysis of organics in drinking water concentrates and advanced waste treatment concentrates. Volume I. NTIS PB85-128221. 

As already mentioned, it is the volatile constituents that serve to identify fruit type and variety. Broadly speaking, qualitative analysis will identify the principal substances present in the volatiles fraction as representative of a particular fruit type, but it is the relative proportions of these substances that will reflect the variety. Alcohols, volatile acids, esters, carbonyl compounds, and low-boiling hydrocarbons are the principal groups represented. Analysis by GC-MS (gas chromatography coupled with mass spectroscopy) can be used to provide quantification and identification of the various constituents. 

GC-MS (gas chromatography-mass spectrometry) is widely used in the analysis of complex mixtures of organic compounds. Such a system is operating with a carrier gas (He) flow through the column of 20 atm ccmin-1 at 293 K. Since the pressure requirements of the GC and the MS differ by several orders of magnitude, two possible systems are considered (see diagrams (a) and (b)). 

Various methods and instruments are available for measuring gas concentrations in fire effluents, e.g., gas detector tubes, ion-selective electrodes, GC/MS (gas chromatography/mass spectrometry), and Fourier Transform Infrared (FTIR) spectroscopy. An extensive review of the methods is provided in ASTM E 800 and ISO 19701. 

US EPA published its initial list of 187 organic compounds found in US drinking water in 1975. Analyses were performed using GC-MS (gas chromatography with mass spectroscopy) and a packed column to separate organic compounds. Present-day analyses using a capillary column to separate compounds have increased the resolution of GC-MS detection several fold (7). 

GC-MS, Gas chromatography-mass spectrometry HHS, Department of Health and Human Services DOT, Department of Transportation DOD, Department of Defense MDA, methylenedioxyamphetamine MDAM, methylenedioxymethamphetamine MDEA, methylenedioxyethylamphetamine PCP, phencyclidine LSD, lysergic acid diethylamide TEfC-COOH, ll-nor-A -tetrahydrocannabinol-9-carboxylic acid. 

Model reaction trials and modem analytical methods (gas chromatography/mass spectrometry (GC/MS), gas chromatography/olfactometry (GC/0)) permitted the identification of key mechanisms responsible for flavour generation in process flavourings and some of the most important ones are detailed below. Often chemically complex precursor raw materials (vegetables such as onions, spices, yeast extracts, animal products) are used. Research work on these complex reactions is rare but necessary and allows the discovery of new key odorants and formation pathways. For example, Widder and co-workers [13] discovered a new powerful aroma compound, 3-mer-capto-2-methylpentan-l-ol in a complex process flavour based on onion. 

Lucas SV. 1984. GC/MS (gas chromatography/mass spectrophotometry) Analysis of organics in drinking water concentrates and advanced waste treatment concentrates, Vol. 2 Computer-printed tabulations of compound identification results for large-volume concentrations. Battelle Laboratories, Columbus, OH for U.S. Environmental Protection Agency, Office of Research and Development, Health Effects Research Laboratories, RTP, NC. Report No. EPA -600/1-84-020A. 397. 

CFR = Code of Federal Regulations CPSC = Consumer Product Safety Commission DNR = Department of Natural Resources DOT = Department of Transportation EL = emissions level EPA = Environmental Protection Agency FDA = Food and Drug Administration GC/MS = gas chromatography/mass spectroscopy ... 

FTIR Fourier transform infrared spectroscopy (technique useful in identifying and analyzing various unknown compounds, such as environmental pollutants) GC Gas chromatography (most commonly used analytical technique for organics) GC/MS Gas chromatography/mass spectrometry (technique based on chromatographic separation, followed by chemical or electron-impact ionization and identification of the mass spectra of the ionized fragments)... 

There are around a dozen GC detectors in common use. Detailed descriptions and illustrations of 16 dilferent types, together with representative application chromatograms, can be accessed at the www.srigc.com site fisted in Appendix 12.1. Spectroscopic instruments can be interfaced to the effluent of a GC and act as a form of detector which has the compound identification power of a spectroscopic measurement. This mating of a separation instrument to a spectroscopic instmment is called a hyphenated technique. The acronyms for the two classes of instruments are separated by a hyphen [or sometimes a slash (/)], as in GC-MS gas chromatography-mass spectrometry. These will be discussed later in Section 12.8. Some of the general characteristics of GC detectors which need to be considered are the following ... 

Inununoassay and GC/MS (gas chromatography/mass spectrometry) analysis for triazine herbicides were compared in order to evaluate the potential of Inununoassay as a screening tool. Water samples were collected at 146 sites on streams In a 10-state region of the midwestern United States during 1989 before and shortly after application of pre-emergent herbicides that were used for weed control in the production of corn and soybeans. The sites were sampled a third time in fall 1989 during a low streamflow period. 

GC-MS Gas chromatography-mass spectrometry. An analytical procednre that combines a gas chromatograph, which separates mixtures of componnds into individnal components, with a mass spectrometer, which breaks the compounds into fragments that indicate the molecular weight and structure of each component. This procedure is one of few that can provide reliable identifications of organic compounds. 

The most infamous case is that of American cyclist Floyd Landis. The story begins on July 20, 2006, when Landis won section 17 of the Tour de France. He was required to undergo a doping test following the race. The level of testosterone in urine is determined by a method called GC-MS (Gas Chromatography— Mass Spectrometry), and is often referred to as the T/E test. Here, T means testosterone, whereas E stands for epitestosterone, which is a variant of the hormone that occurs in the body but has none of its effects. In most humans, the T/E ratio is about 1. The... 

The explanation of the biosynthetic pathway may also be possible through molecular biology techniques that use mutants. The use of tandem analytical instrumentation (e.g., GC/MS (gas chromatography/mass spectrometry), NMR/MS, LC/MS (liquid chromatography/mass spectrometry)) has improved the identifications of primary and secondary metabolites. 

GALDl Graphite-assisted laser desorphon and ionizahon GC/MS Gas chromatography/mass spectrometry... 

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