GC or gas-liquid chromatography

For more detail on apparatus and chromatographic colurrms see http //www.sigmaaldrich.com/analytical-chromatography/gas-chromatography. html and websites at the end of the section on HPLC below. 

In contrast to vapour phase chromatography, the mobile phase in liquid chromatography is a liquid. In general, there are four main types of liquid chromatography adsorption, partition, ion-chromatography, and gel fUtration. 

When the gas chromatograph is attached to a mass spectrometer, a very powerful analytical tool (gas chromatography-mass spectrometry, GC-MS) is produced. Vapour gas chromatography allows the analyses of mixtures but does not allow the definitive identification of unknown substances whereas mass spectrometry is good for the identification of a single compound but is less than ideal for the identification of mixtures of 

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Gas chromatography (GC) or gas liquid chromatography (GLC) as a method for analysis of K vitamins is not used as frequently as for other compounds of biochemical interest (e.g., determination of fatty acids). The main reason of this fact can be seen in a possible degradation of the vitamin K molecules on the heated GC-columns. Lefevere et al. [2] and Lambert et al. [17] reviewed early GC methods, where among other things electron capture detection was used for determination of VKl and VK epoxide. 

GLC or GC. The acronyms stand for gas-liquid and gas chromatography. The original packings were either a solid or a solid coated with a liquid. The mobile phase is a gas, hence the term gas or gas-liquid chromatography. The liquid is usually forgotten. 

Gas chromatography (GC) a. Gas-liquid chromatography (GIX) Liquid adsorbed or bonded to a solid surface Partition between gas and liquid... 

Residual monomers in SAN have been a growing environmental concern and can be determined by a variety of methods. Monomer analysis can be achieved by polymer solution or directly from SAN emulsions (27) followed by "head space" gas chromatography (gc) (28,29). Liquid chromatography (Ic) is also effective (30). 

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. 

Several methods can be used for the residue analysis of anilides, especially gas chro-matography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS). GC/ECD or GC/NPD for the determination of anilides has generally been used except for the unstable metabolites of naproanilide and clomeprop, which are determined by HPLC/UV, HPLC/FL or GC/ECD after derivatization. 

Ethylenethiourea (ETU) is a toxic decomposition product/metabolite of alky-lenebis(dithiocarbamates). This compound could be generated during processing of treated crops at elevated temperature. Different chromatographic methods to determine the residue levels of ETU have been published. After extraction with methanol, clean-up on a Gas-Chrom S/alumina column and derivatization (alkylation) with bro-mobutane, ETU residues can be determined by GC with a flame photometric detector in the sulfur mode. Alternatively, ETU residues can also be determined by an HPLC method with UV detection at 240 nm or by liquid chromatography/mass spectrometry (LC/MS) or liquid chromatography/tandem mass spectrometry (LC/MS/MS) (molecular ion m/z 103). ... 

The extracted fractions were esterified with either BF3-MeOH reagent or diazomethane and analyzed by GLC. Gas liquid chromatography (GLC) was conducted with a Perkin-Elmer Sigma 3 equipped with flame ionization detector. Separations were obtained on a Hewlett Packard 12 m x 0.2 mm i.d. capillary column coated with methyl silicon fluid (OV-101). The temperature was maintained at 80°C for 2 min then programmed from 80 to 220°C at 8°C/min. The injector temperature was 250°C. Mass spectra were obtained on a Hewlett Packard model 5995 GC-MS mass spectrometer, equipped with a 15 m fused silica capillary column coated with 5% phenyl methyl silicone fluid. Spectra were obtained for major peaks in the sample and compared with a library of spectra of authentic compounds. 

Gas-Liquid Chromatography. In gas-liquid chromatography (GLC) the stationary phase is a liquid. GLC capillary columns are coated internally with a liquid (WCOT columns) stationary phase. As discussed above, in GC the interaction of the sample molecules with the mobile phase is very weak. Therefore, the primary means of creating differential adsorption is through the choice of the particular liquid stationary phase to be used. The basic principle is that analytes selectively interact with stationary phases of similar chemical nature. For example, a mixture of nonpolar components of the same chemical type, such as hydrocarbons in most petroleum fractions, often separates well on a column with a nonpolar stationary phase, while samples with polar or polarizable compounds often resolve well on the more polar and/or polarizable stationary phases. Reference 7 is a metabolomics example of capillary GC-MS. 

Gas liquid chromatography (GLC) or gas chromatography (GC) finds its abundant applications in the accurate and precise analysis of plethora of official pharmaceutical substances covering a wide range as enumerated below ... 

Gas chromatography (GC) employs a gaseous mobile phase, known as the carrier gas. In gas-liquid chromatography (GLC) the stationary phase is a liquid held on the surface and in the pores of a nominally inert solid support. By far the most commonly used support is diatomaceous silica, in the form of pink crushed firebrick, white diatomite filter aids or proprietary variants. Typical surface areas of 0.5-4 m2/g give an equivalent film thickness of 0.05-1 pm for normal liquid/support loadings of 5-50 per cent by mass. 

Measurements of the common physical constants such as boiling point or refractive index are not sufficiently sensitive to determine the trace amounts of impurities in question. Besides the common spectroscopic methods, techniques like gas chromatography (GC), high-pressure liquid chromatography (HPLC), or thin-layer chromatography (TLC) are useful. The surest criterion for the absence of interfering foreign compounds lies in the polymerization itself the purification is repeated until test polymerizations on the course of the reaction under standard conditions are reproducible (conversion-time curve, viscosity number of the polymers). 

Sadana and Gaonkar have simultaneously determined diloxanide furoate and tinidazole in pharmaceutical dosage form by gas liquid chromatography [37]. Powdered tablets or suspension formulations were dissolved in chloroform, the solution filtered, and then diluted to 25 mL with chloroform. The solution also contained metronidazole as an internal standard. A 600 nL aliquot was analyzed on a stainless steel column (1 m X 3.2 mm) containing 3% of OV-17 on Chlorosorb W-UP (100-120 mesh). The GC system was operated at 200°C, using nitrogen as the carrier gas (45 mL/min). Flame ionization detection was used to observe the analytes. 

The method of complete electrolysis is also important in elucidating the mechanism of an electrode reaction. Usually, the substance under study is completely electrolyzed at a controlled potential and the products are identified and determined by appropriate methods, such as gas chromatography (GC), high-performance liquid chromatography (HPLC), and capillary electrophoresis. In the GC method, the products are often identified and determined by the standard addition method. If the standard addition method is not applicable, however, other identification/determination techniques such as GC-MS should be used. The HPLC method is convenient when the product is thermally unstable or difficult to vaporize. HPLC instruments equipped with a high-sensitivity UV detector are the most popular, but a more sophisticated system like LC-MS may also be employed. In some cases, the products are separated from the solvent-supporting electrolyte system by such processes as vaporization, extraction and precipitation. If the products need to be collected separately, a preparative chromatographic method is use-... 

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