Gas adsorption chromatograph

Volatilization processes, combined with gas adsorption chromatographic investigations, are well established methods in nuclear chemistry. Fast reactions and high transport and separation velocities are crucial advantages of these methods. In addition, the fast sample preparation for a-spectroscopy and spontaneous fission measurements directly after the gas-phase separation is a very advantageous feature. Formation probabilities of defined chemical compounds and their volatility can be investigated on the basis of experimentally determined and of predicted thermochemical data, the latter are discussed in Part II of this chapter. 

The formalism can easily be adapted to a PC-based program for an evaluation of the AH°ads from gas adsorption chromatographic results and, vice versa, to predict the behavior of an adsorbate in gas chromatography from its known adsorption data. The formulas used in the PC-based simulation are given here. For their derivations see [17]. 

Due to the extremely low production rates of transactinides in the nuclear fusion reactions, the chemical characterizations are carried out on a single atom level. The chemical reaction products are characterized on the basis of their behavior in the separation process or, exactly speaking, in the gas adsorption chromatographic process. In this process the formation probability of defined chemical states of transactinides and the subsequent interaction of the formed molecules with a solid state surface are studied. 

The experimental proof of such correlations for defined classes of pure substances is essentially for the prediction of adsorption properties of transactinides and their compounds. Therefore, a variety of gas adsorption chromatographic experiments were carried out with carrier free amounts of different radioisotopes using selected modified surfaces as stationary phases. The use of carrier free amounts is necessary to experimentally obtain adsorption conditions at nearly zero surface coverage. 

The net adsorption enthalpies and the predicted sublimation enthalpies (see Method 1) were used to calculate the adsorption enthalpies of transactinides on selected metal surfaces (Method 11). The metals, which are presented in Table 4, can be used as stationary phase in gas adsorption chromatographic experiments for selective gas chemical separations or, in the case of high adsorption interaction, as strong fixation materials for the sample preparation in the measurement of transactinides. 

Analysis of Blood Gases with Gas Adsorption Chromatographic Techniques J. Appl. Physiol. 16 374-377 (1961) ... 

The stability and the volatility are chemical properties that define the behavior of a transactinide element or its compound in the gas-adsorption chromatographic process. Therefore, the predictions of these properties are instrumental for the design of experiments (see Chapter Experimental Techniques for instmmental aspects) and they are also indispensable for the interpretation of experimental... 

Eichler, B. The behaviour of radionuclides in gas adsorption chromatographic processes with superimposed chemical reactions (chlorides). Radiochim. Acta 72, 19-26 (1996)... 

Gas chromatography, depending on the stationary phase, can be either gas—Hquid chromatography (glc) or gas—soHd chromatography (gsc). The former is the most commonly used. Separation in a gas—Hquid chromatograph arises from differential partitioning of the sample s components between the stationary Hquid phase adsorbed on a porous soHd, and the gas phase. Separation in a gas—soHd chromatograph is the result of preferential adsorption on the soHd or exclusion of materials by size. 

The great leap forward for chromatography was the seminal work of Martin and Synge (7) who in 1941 replaced countercurrent liquid-liquid extraction by partition chromatography for the analysis of amino acids from wool. Martin also realized that the mobile phase could be a gas rather than a liquid, and with James first developed (8) gas chromatography (GC) in 1951, following the gas-phase adsorption-chromatographic separations of Phillips (9). 

Adsorption, a surface phenomenon, is the basis of many gas or liquid mixture separation and purification methods. It is also the basis of adsorption chromatographic methods used for the analysis of complex mixtures. The knowledge of adsorption mechaiusms is useful in choosing the suitable systems providing optimum separation. 

Procedures for determining fatty acids in sediments involved liquid-liquid extraction, liquid-solid adsorption chromatography followed by gas liquid chromatographic analysis [10-12], Liquid extractions have been performed with methanol-chloroform [13], methylene chloride [14] and benzene-methanol [15, 16]. Typical liquid-solid adsorbents are silicic acid. Standard gas chromatographic separations for complex mixtures employ non-polar columns packed with OV-1, OV-17, OV-101, SE-30, or glass capillary columns containing similar phases. 

Sulfur compounds in the gas oil fractions from two bitumens (Athabasca oil sand and Cold Lake deposit)> a heavy oil (Lloydminster) from Cretaceous reservoirs along the western Canada sedimentary basin, and a Cretaceous oil from a deep reservoir that may be mature (Medicine River) are investigated. The gas oil distillates were separated to concentrates of different hydrocarbon types on a liquid adsorption chromatographic column. The aromatic hydrocarbon types with their associated sulfur compounds were resolved by gas chromatographic simulated distillation and then by gas solid chromatography. Some sulfur compounds were further characterized by mass spectrometry. The predominant sulfur compounds in these fractions are alkyl-substituted benzo- and dibenzothiophenes with short side chains which have few dominant isomers. 

In adsorption chromatography the mobile phase is usually a liquid and the stationary phase is a finely-divided solid adsorbent (liquid-solid chromatography). Separation here depends on the selective adsorption of the components of a mixture on the surface of the solid. Separations based on gas-solid chromatographic processes are of limited application to organic mixtures. The use of ion-exchange resins as the solid phase constitutes a special example of liquid-solid chromatography in which electrostatic forces augment the relatively weak adsorption forces. 

Gas-Phase Adsorption Chromatographic Determination of Thermochemical Data and Empirical Methods for their Estimation... 

Part I Basic principles of the determination of adsorption properties using gas-phase adsorption chromatographic methods... 

This chapter describes basic physico-chemical relations between the gas phase transport of atoms and molecules and their thermochemical properties, which are related to the adsorption-desorption equilibrium. These methods can either be used to predict the behavior of the adsorbates in the chromatographic processes, in order to design experiments, or to characterize the absorbate from its experimentally observed behavior in a process. While Part I of this chapter is devoted to basic principles of the process, the derivation of thermochemical data is discussed in Part n. Symbols used in the following sections of Part I are described in Section 5. For results, which were obtained applying the described evaluation methods in gas-adsorption chromatography, see Chapters 4 and 7 of this book. 

Selective gas adsorption. The gas chromatographic technique can be cited as another example of rapid radioactive gas separation. One procedure for the separation and detection of argon, krypton and xenon activities In the coolant or exhaust gases from nuclear facilities utilizes such a method (150). 

None of the commercial process simulators contains a good library model for adsorptive separations or membrane separations at the time of writing. These separation methods are important for gas-gas separations, chromatographic separations, and size-exclusion or permeation-based separations. All of these processes must be modeled using component splitters, as described next. 

Eichler B, Eichler R (2003) Gas-phase adsorption chromatographic determination of thermochemical data and empirical methods for their estimation. In Schadel M (ed) The chemistry of superheavy elements. Kluwer, Dordrecht, p 205... 

The pioneering gas-liquid chromatographic studies in the early 1950s were carried out on packed columns in which the stationary phase was a thin film of liquid retained by adsorption on the surface of a finely divided, inert solid support. From theoretical studies made during this early period, it became apparent that unpacked columns having inside diameters of a few tenths of a millimeter could provide separations that were superior to those of packed columns in both speed and column efficiency. In such capillary columns, the stationary phase was a film of liquid a few tenths of a micrometer thick that uniformly coated the interior of capillary tubing. In the late 1950s, such open tubular columns were constructed the predicted... 

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