Gas-solid adsorption capillary columns

Several gas-solid adsorption capillary columns are available. They are commonly called porous-layer open tubular or PLOT columns. These columns contain a layer of adsorbent particles coated on the irmer wall of the fused silica tubing. Phases of aluminum oxide (alumina), molecular sieves, and porous polymers (Poraplot-like) are commercially available. Gas-solid adsorption rather than a gas-liquid partition is the separation mechanism involved. PLOT columns are well suited for the analysis of light hydrocarbons, sulfur gases, permanent gases, or other very volatile solutes at or... 

Gas-Solid Adsorption Capillary Columns (PLOT Colnmns)... 

There are two types of GC gas-solid (adsorption) chromatography and gas-liquid (partition) chromatography. The more important of the two is gas-liquid chromatography (GLC), used in the form of a capillary column. In this chapter, we describe the principles of operation of gas chromatography, the types of GC columns, and GC detectors. The principles of mass spectrometry (MS) are described, along with coupling of the gas chromatograph with a mass spectrometer (GC-MS). 

In general the ALOT column will have relatively high optimum carrier gas velocities due to the fast kinetics of the gas-solid adsorption mechanism and the relatively small compounds to be analyzed. This was also found on AlgOg coated fused silica columns where the optimum carrier gas velocity was found to be a factor 2.5 higher than with normal gas-llquid capillary chromatography. 

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. 

Gas chromatography may be divided into gas solid chromatography (mainly adsorptive processes) and gas-liquid chromatography (mainly partition) depending on whether the stationary phase is a solid or a liquid at its operating temperature. If the stationary phase is a hquid it must be coated on a support for packed coliunn chromatography. For capillary column chromatography, the stationary phase may be coated directly on to the walls of the coliunn, or on to a support which is bonded to the... 

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... 

The difference in the adsorption isotherms of isotopic molecules has long been known and it has been used for isotope separation and isotope analysis. For example, deuterium gas exhibits an enrichment factor of 40 ( ) at 20 K on silica gel, but the enrichment factor decreases steeply with increasing temperature (Krumbiegel 1970). Another example is the behavior of CH4/CD4 system in a capillary column with activated glass surface at 153 K the retention time of CH4 is larger than that of CD4, at 130 K they are equal to each other and at lower temperatures CH4 leaves earlier the column than CD4 (Bruner et al. 1966). Similarly to the gas-solid chromatographic separations, gas-liquid separation techniques have also been widely used for isotopic separation and for rapid and convenient analysis of mixtures of... 

For the first time, an attempt has now been made to present a consistent treatment of gas-solid capillary chromatography. This technique employs an open-tubular column with a solid sorbent layer present on the inner wall. Capillary gas adsorption columns are now in routine laboratory use. They are important for analysing gases (including isotopes) and light volatile compounds in chemistry, chemical engineering, petrochemistry, medicine, pharmacy, food science, environmental pollution control, and many more. 

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