Gas chromatographic parameters

Meier Augenstein, W., Watt, P. W. and Langhans, C. D. (1996) Influence of gas chromatographic parameters on the measurement of 13C/12C isotope ratios by gas liquid chromatography combustion isotope ratio mass spectrometry. I. Journal of Chromatography, A 752, 233 241. 

Reliable flame photometric detector quantification of organosulphur compounds requires careful optimization of the gas chromatograph parameters. Although the relative response of the flame photometric detector to various sulphur compounds remains somewhat controversial [7], analysis of organosulphur compounds by flame photometric detector is now relatively straightforward. 

GAS CHROMATOGRAPHIC PARAMETERS. A gas chromatograph equipped with a hydrogen flame detector is used. Flame ionization detection allows the use of samples containing water. The column is stainless steel (6 ft x 0.25 in. o.d.) packed with 30° Carbowax 20 M on acid-washed 60/80 mesh Chromosorb W. The column was conditioned overnight at 180°C with a flow of nitrogen carrier gas. 

P. Liras, Thin-layer and gas chromatographic parameters of morphine and ccodeine derivatives, J. Chromatogr., 706 238 (1975). 

Larose and Chau [189] state that owing to the similar retention times of several common phenoxyacetic acid type herbicides the alkyl esters are subject to incorrect identification if several herbicides are present. Also, the sensitivity obtainable by means of electron capture detection of the alkyl esters by some herbicides, such as MCPA and MCPB is very poor and therefore the method is generally not suitable for the determination of these compounds in water. In addition, the methyl ester of MCPA has a very short retention time close to the solvent front and is prone to interference from sample coextractives, which usually appear in this region. In fact the MCPA methyl ester often cannot be detected even at higher levels because of overlapping with coextraction peaks when the same gas chromatographic parameters as for the determination of organochlorine pesticides are used. Hence other derivatives have been considered. 

Liras 3 used an OV-17 column for Investigations on the metabolism of morphine and codeine by Arthrobacter species, and gave the gas chromatographic parameters of eight oxidized compounds, found as metabolites (14-hydroxymorphine, 14-hydroxymorphinone, 14-hydroxydihydro-morphinone, dihydromorphinone, codeinone, 14-hydroxycodeine, 14-hydroxycodeionone and 14-hydroxydihydrocodeinone). 

Voelkel, A. and Fall, (. (1995) Influence of prediction method of the second virial coefficient on inverse gas chromatographic parameters. J. Chromatogr. A, 721,... 

A 1.1 The logarithmic Kovats Retention Index is a gas chromatographic parameter characteristic of a solute s relative retention on a specified liquid phase at a specified (isothermal) temperature. It is a very useful tool in the qualitative identification of chromatographic peaks. 

Nevertheless, a number of gas chromatographic applications exist, epecially those for the determination of crude oil indicators. Such indicators are used as geochemical parameters for the thermal history of the crude as well as to indicate the possible relationship between crudes from different wells. These indicators comprise a number of isomeric aromatic species, such as the individual alkylnaphthalenes (44, 45), the individual Cio-mono-aromatics or the individual C9-mono-aromatics. The ratio between these isomers gives a definite indication of the crude oil. In general, these systems use a Deans switching unit to make a heart-cut, which then is focused, reinjected and separated on a second column with a different polarity. 

The net retention volume and the specific retention volume, defined in Table 1.1, are important parameters for determining physicochemical constants from gas chromatographic data [9,10,32]. The free energy, enthalpy, and. entropy of nixing or solution, and the infinite dilution solute activity coefficients can be determined from retention measurements. Measurements are usually made at infinite dilution (Henry s law region) in which the value of the activity coefficient (also the gas-liquid partition coefficient) can be assumed to have a constant value. At infinite dilution the solute molecules are not sufficiently close to exert any mutual attractions, and the environment of each may be considered to consist entirely of solvent molecules. The activity... 

Mackay, D., Shiu, W. Y., Wolkoff, A. W. (1975) Gas chromatographic determination of low concentration of hydrocarbons in water by vapor phase extraction. In Water Quality Parameters. ASTM STP 573, pp. 251-258, American Society for Testing and Materials, Philadelphia, PA. 

When a GC 16A series gas chromatograph is used as the core, various laboratory-automation-oriented attachments such as bar-code reader and a magnetic-card reader become compatible a labour-saving system can be built, in which the best operational parameters are automatically set. Each satellite gas chromatograph (GC 14A series) operates as an independent instrument when a keyboard unit is connected. 

GC-Computer System Nowadays, a large number of data-processing-computer-aided instruments for the automatic calculation of various peak parameters, for instance relative retention, composition, peak areas etc., can be conveniently coupled with GC-systems. A commercially available fairly sophisticated computer system of such type are available abundantly that may be capable of undertaking load upto 100 gas-chromatographs with ample data-storage facilities. In fact, the installation such as multi GC-systems in the routine analysis in oil-refineries and bulk pharmaceutical industries, and chemical based industries have tremendously cut-down their operating cost of analysis to a bare minimum. 

Procedure First of all maintain the above experimental parameters of the gas chromatograph and then maintain the six solutions at 90 °C for 20 minutes, pressurise for a duration of 30 seconds only and transfer subsequently to the column at a temperature of 120 °C. Repeat the operation using a vial containing 1 ml of water. Perform each measurement at least three times. 

Burtiset al, 1987). Current gas chromatographs have the capability of very complex temperature programs that can minimize the time per run and maximize the resolution of the compounds of interest. The minimum and maximum temperatures are usually the only nonvariable parameters. The solvent usually determines the minimum temperature because it must be volatized for sample introduction. The maximum temperature is determined by the stationary phase, because it may break down at high temperatures, which can result in an elevated baseline of the chromatograph. Thus, the manufacturer recommends a maximum temperature to maximize column life and minimize breakdown. 

Przyjazny, A., Janicki, W., Chrzanowski, and Staszewki, R. Headspace gas chromatographic determination of distribution coefficients of selected organosulphur compounds and their dependence of some parameters, J. Chromatogr. A, 280 249-260, 1983. 

Several studies attempted to relate the partition coefficient P of a solute in a liquid chromatographic or a gas chromatographic system with the composition of the two phases, one of which has a varying composition [19-23]. Tijssen et al. [24] and Schoenmakers [25] derived a relation between the partition coefficient and a binary mobile phase in reversed-phase HPLC from the solubility parameter theory of Hildebrand et al. [26]. Similarly, a relation can be derived for liquid-liquid extraction with extraction liquids composed of three components ... 

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