G-------------------------------------Gas chromatography

Analyses of gases and vapours tend to utilize the techniques described on page 308. Many of these methods were traditionally limited to laboratory analyses but some portable instruments are now available for, e.g., gas chromatography (Table 10.16) and non-dispersive infra-red spectrometry (Table 10.17). 

In modern times, most analyses are performed on an analytical instrument for, e.g., gas chromatography (GC), high-performance liquid chromatography (HPLC), ultra-violet/visible (UV) or infrared (IR) spectrophotometry, atomic absorption spectrometry, inductively coupled plasma mass spectrometry (ICP-MS), mass spectrometry. Each of these instruments has a limitation on the amount of an analyte that they can detect. This limitation can be expressed as the IDL, which may be defined as the smallest amount of an analyte that can be reliably detected or differentiated from the background on an instrument. 

Mass spectrometry is used to identify unknown compounds by means of their fragmentation pattern after electron impact. This pattern provides structural information. Mixtures of compounds must be separated by chromatography beforehand, e.g. gas chromatography/mass spectrometry (GC-MS) because fragments of different compounds may be superposed, thus making spectral interpretation complicated or impossible. To obtain complementary information about complex mixtures as a whole, it may be advantageous to have only one peak for each compound that corresponds to its molecular mass ([M]+). Even for thermally labile, nonvolatile compounds, this can be achieved by so-called soft desorption/ionisation techniques that evaporate and ionise the analytes without fragmentation, e.g. matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS). 

In this paper, data is cited which demonstrates that diffusional monitoring can be used in circumstances in which pumps and charcoal tubes were previously used. The data cited emphasizes the comparability of diffusional monitoring to charcoal tube and pump. However, it must be noted that the methods are different, and will not in each circumstance yield comparable results. The most conclusive tests will be those which employ a third method (e.g., gas chromatography, infrared analysis) capable of accurately determining the contaminant, or contaminants concentration. 

Vrandi-Piskou, D., Parissakis, G. Gas chromatography of the first members of the homologous serie SinCl2n+2. J. Chromatog. 22, 449 (1966). 

Jacquelot, P., Thomas, G. Gas chromatography of vanadyl trifluoroacetylacetonate. Bull. Soc. Chim. France 1970, 3167. 

High-pressure liquid chromatography (HPLC) has grown into a powerful separation technique routinely applied for the separation of a variety of compounds in a variety of matrices [1], Despite its success, HPLC may still be regarded as a relatively inefficient technique, certainly when compared to, e.g., gas chromatography (GC) or capillary electrophoresis (CE). 

Faniewski, K., Wannman, T., Hagman, G. Gas chromatography with mass spectrometric, atomic emission and Fourier transform infrared spectroscopic detection as complementary analytical techniques for the identification of unknown impurities in pharmaceutical analysis. J. Chromatogr. A 985, 275-282 (2003)... 

Lewisite is reported to possess a characteristic (geraniumlike) odor in the range of 0.8 mg/m to more commonly cited 14-23 mg/m median detection (Pechura and Rail, 1993). US forces have detectors for lewisite-paper and kits (M7 and M9A). Other forensic techniques for soil and material analysis already exists (e.g. gas chromatography). In biological tissues, increased arsenic levels are a surrogate for lewisite (Haddad and Wincester, 1983). 

There are a variety of analytical methods commonly used for the characterization of neat soap and bar soaps. Many of these methods have been published as official methods by the American Oil Chemists Society (23). Additionally, many analysts choose United States Pharmacopoeia (USP), British Pharmacopoeia (BP), or Food Chemical Codex (FCC) methods. These methods tend to be colorimetric, potentio-metric, or titrametric procedures. However, a variety of instrumental techniques are also frequently used, e.g., gas chromatography, high-performance liquid chromatography, nuclear magnetic resonance spectroscopy, infrared spectroscopy, and mass spectrometry. 

Schomhurg, G. Gas Chromatography, A Practical Course, VCH Verlagsgesellschaft Weinheimd, 1990. 

Because of its high specificity and simplicity, the enzymatic method is the method of choice for measuring lactate, although other methods may also be used (e.g., gas chromatography and photometry). 

N4. Nikelly, J. G., Gas chromatography of free fatty acids. Anal. Chem. 36, 2244-2248 (1964). 

Chen, Y. C. and Lo, J. G., Gas chromatography with flame ionization and flameless sulfur chemiluminescence detectors in series for dual channel detection of sulfur compounds, Chromatographia, 43, 522-526, 1996. 

Bnmmark, P., Dalene, M., and Skarping, G., Gas-chromatography negative-ion chemical-ionization mass-spectrometry of hydrolyzed human urine and blood-plasma for the biomonitoring of occupational exposure to 4,4 -methylenebisaniline, Analyst, 120, 41-45, 1995. 

Because the IV is a measure of the relative unsaturation of a compound or sample, other analytical techniques (e.g., gas chromatography of FA composition, AOCS Cd lc-85) can be used to estimate the value. Interest in recent years has focused on spectroscopic techniques for the rapid determination of TV. Fourier transform (FT)-near-infrared, near-infrared, FT-Raman, and H and nuclear magnetic resonance (NMR) spectroscopic techniques have all been investigated (Ng and Gee, 2001). The most promising results have been obtained with FT-near-infrared spectroscopy, which only takes a few minutes to determine the iodine value (Cox et al., 2000). 

Chromatography is one of the most important methods for direct studies of molecular and chiral recognition by CyDs. Today it has split into several branches, e.g. gas chromatography, GC, high-performance liquid chromatography, HPLC, and capillary electrophoresis and other electromigration techniques, that enable us not only to detect the recognition but also to estimate the complex stoichiometry and formation constant and, consequently, the enthalpies and entropies of complex for-... 

Technique a scientific principle or specific operation, (e.g., gas chromatography-electron-capture detector, GC ECD, Florisil column cleanup or so-called Webb and McCall quantitation. 

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