Flow, gas chromatography

Agathonos, P. Karaiskakis, G., "Thermodynamic Study of Polymer-Solvent Systems by Reversed-Flow Gas Chromatography," J. Appl. Polym. Sci., 37, 2237 (1989). 

For example, little is known about the isotopic composition of formaldehyde in the atmosphere. Formaldehyde is a chemical intermediate in hydrocarbon oxidation. The carbon (8 C) and hydrogen (8D) isotopic composition of atmospheric formaldehyde is analyzed using continuous flow gas chromatography isotope ratio mass spectrometry." Isotope ratios were measured using GC-IRMS (Finnigan MAT 253 stable isotope ratio mass spectrometer, single-sector field with electron impact ion source and multiple ion collection) with a precision of 1.1 and 50%(lo ) for 8 C and 8D, respectively. The accuracy of the online continuous flow isotope technique was verified by calibrating three aliquots of the gas phase standard via the offline dual inlet IRMS technique. The concentration of formaldehyde in ambient air was determined on IRMS major ion peak areas (i.e., mass 44 for 8 C and mass 2 for 8D)." ... 

Catalyst Characterization by Reversed Flow Gas Chromatography Dimitrios Gavril... 

Reversed-flow gas chromatography is another gas chromatographic technique based on the perturbation of the carrier gas flow, which has been utilized for the measurement of physicochemical parameters. The fundamental difference of RF-GC from classical GC is the use of a T-form system of chromatographic columns (sam-phng and diffusion columns) placed perpendicularly, one... 

Reversed-flow gas chromatography methodologies have been utilized for the investigation of various catalytic processes, and a large number of physicochemical quantities related to the kinetics of the elementary steps (adsorption, desorption, surface reaction) and the nature of the active sites have been determined. These parameters are summarized as follows ... 

Gavril, D. Reversed flow gas chromatography A tool for instantaneous monitoring of the concentrations of reactants and products in heterogeneous catalytic processes. J. Liq. Chromatogr. Relat. Technol. 2002, 25 (13-15), 2079-2099. 

Reversed-flow gas chromatography (RF-GC) has been used to study the kinetics of surface-catalyzed reactions and the nature of the active sites. RF-GC is technically very simple and it is combined with a mathematical analysis that gives the possibility for the estimation of various physicochemical parameters related to catalyst characterization in a simple experiment under conditions compatible with the operation of real catalysts. The experimental findings of RF-GC for the oxidation of CO over well-studied silica-supported platinum-rhodium bimetallic catalysts are in agreement with the results of other workers using different techniques ascertaining that RF-GC methodologies can be used for the characterization of various solids with simplicity and accuracy. 

Table 1 Rate constants for the adsorption (fei), desorption (fe i), and disproportionation reaction ( 2) of carbon monoxide over a Pt/ Si02 catalyst, determined by reversed-flow gas chromatography, at...

Gavril, D. Reversed flow gas chromatography A tool for instantaneous monitoring of the concentrations of reactants... 

Gavril, D. Koliadima, A. Karaiskakis, G. Adsorption studies of gases on Pt-Rh bimetallic catalysts by reversed flow gas chromatography. Langmuir 1999,15, 3798-3806. 

Yang, F. Hawkes, S. Lindstrom, F.T. Determination of precise and reliable gas diffusion coefficients by gas chromatography. J. Am. Chem. Soc. 1976, 98, 5101-5107. Katsanos, N.A. Karaiskakis, G. Vattis, D. Diffusion coefficients fi"om stopped-flow gas chromatography. Chromatographia 1981,14, 695-698. 

Katsanos, N.A. Georgiadou, I. Reversed-flow gas chromatography for studying heterogeneous catalysis. J. Chem. Soc. Chem. Commun. 1980, 5, 242-243. 

Katsanos, N.A. Karaiskakis, G. Reversed-flow gas chromatography applied to physicochemical measurements. Adv. Chromatogr. 1984, 24, 125-180. 

Katsanos, N.A. Kapolos, J. Diffusion coefficients of gases in liquids and partition coefficients in gas-liquid interphases by reversed-flow gas chromatography. Anal. 

The reversed-flow gas chromatography (RFGC) technique, a subtechnique of the inverse gas chromatography (IGC), can be used for the determination of physicochemical quantities pertaining to environment and pollutants. Experimental setup and appropriate mathematical analysis for the calculation of physicochemical parameters are reviewed, taking into account i) the interaction between air pollutant(s) and a solid surface in the absence, or in the presence, of a chemical reaction between two pollutants in the gas phase over the solid material (synergistic effects) and ii) exchange of gas pollutant(s) between atmospheric and water environment. 

Reversed-flow gas chromatography, which is a subtechnique of inverse gas chromatography, can be applied to determination of necessary physicochemical quantities for the interaction between air pollutants and cultural objects and exchange of air pollutants between atmospheric and water environments. 

Kalantzopoulos, A. Abatzoglou, C. Roubani-Kalantzopoulou, F. Environmental catalysis studied by the reversed-flow gas chromatography. Measurements, mechanism and models. Colloids Surf. 1999,151,377-3S7. 

Reversed-flow gas chromatography (RF-GC) has been successfully used to characterize solid catalysts under conditions compatible with the operation of real catalysts. RF-GC is not limited to chromatographic separation since RF-GC is accompanied by suitable mathematical analysis of the chromatographic data, the simultaneous determination of various physicochemical parameters is possible. Thus, various catalytic processes related to the operation of fuel cell units such as steam reforming, catal3dic partial oxidation, autothermal reforming, as well as water-gas shift (WGS) reaction and selective CO oxidation can be studied. 

In conventional GC a gaseous mobile phase flows in a defined direction over a stationary phase or packing, resulting in the selective retention of solute components. In reversed-flow gas chromatography (RF-GC) the system is modified another column (diffusion column) is placed perpendicularly in the center of the chromatographic... 

Fig. 1 Experimental setup used by reversed-flow gas chromatography for the characterization of solid catalysts a) under steady-state conditions, with catalyst bed being put at a short length of sampling column I, near the junction of diffusion and sampling columns b) under non-steady-state conditions, with catal riic bed being put at the top of diffusion column L.

During the last 25 years, a gas flow perturbation technique has been used for physicochemical measurements in homogeneous and heterogeneous systems. This technique is reversed-flow gas chromatography (RF-GC). In this entry, the basic theoretical principles, the experimental setup, and the applications of this technique are reviewed. 

Reversed Flow Gas Chromatography was introduced in its preliminary form in 1980 by Professor N. A. Katsanos and his colleagues at the University of Patras.Until now, more than on 100 original articles, five reviews, and two books have been published referring to this technique and its applications. 

Reversed Flow Gas Chromatography has been used to smdy the kinetics of various surface-catalyzed reactions, as well as for other physicochemical measurements. The experimental setup is given in Fig. Ic where, near the closed end of the diffusion column, a small amount of solid is placed and the length of this section is denoted as L2, while the solute A is injected by means of an injection port. 

Karaiskakis, G. Katsanos, N.A. Niotis, A. Measurement of diffusion coefficients in multicomponent gas mixtures by the reversed-flow gas chromatography. Chromatographia 1983,17, 310-312. 

Flux of gases across the air-water interface studied by 19. reversed-flow gas chromatography. J. Chromatogr. A,... 

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