Packed column in gas chromatography

In recent years, many of the technologically outdated methods of 40 CFR Part 136 have been upgraded to incorporate the latest advances in instrumental analysis. For example, capillary chromatographic columns with superior compound resolution replaced obsolete packed columns in gas chromatography (GC) and GC/MS analytical methods Freon 113, a chlorofluorocarbon harmful to the environment, was phased out as the extraction solvent in oil and grease analysis and replaced with hexane in Method 1664 (EPA, 1999b). 

W. R. Supina, The Packed Column in Gas Chromatography, Bellefonte, Pennsylvania, Supeico, 1974. 

A packed column in gas chromatography had an inside diameter of 5.0 mm. The measured volumetric flow rate at the column outlet was 50 mL/min. If the column porosity was 0.45, what was the linear flow velocity in cm/s ... 

W. Supina, T7te Packed Column in Gas Chromatography, Supelco, Bellefonte, PA, U.S.A., 1974. 

Supina V.R. The Packed Columns in Gas Chromatography. Supelco Inc., Bellefonte, Pennsylvania, 1974. 

The interested reader desiring further details about solid supports is urged to consult the comprehensive reviews of Ottenstein (10,11) and the benchmark book, The Packed Column in Gas Chromatography, written by Supina (12). 

As with any form of chromatography, the separating efficiency of capillary columns in gas chromatography is strongly dependent on the column stationary phase, carrier gas flow rate, and temperature. Because of the high separation efficiency of capillary columns, only a limited number of stationary phases can be substituted for the numerous phases used in most packed column applications. The choice of a stationary phase is commonly dictated by experience. A phase that has been successfully used by others is usually a good choice. Fre-... 

C22. Cramers, C. A., Rijks, J. A., and Bocek, P., Packed versus capillary columns in gas chromatography. Clin. Chim. Acta 34, 159-168 (1971). 

Rate theory is a more realistic description of the processes at work inside a column which takes account of the time taken for the solute to equilibrate between the two phases. It is the dynamics of the separation process which is concerned. The first kinetic equation for packed columns in gas phase chromatography was proposed by Van Deemter. 

High Speed Capillary SFC. Until recently the practice of SFC was restricted to packed columns (17,20-26.43). Capillary colusins are clearly superior for most applications in gas chrootatography, while packed columns in liquid chromatography have tremendous advantages compared to open tubular capillary columns due to the small column diameter (< 10 ym) required to produce equivalent separations (44). Since supercritical fluids have properties intermediate between those of a gas and those of a liquid, one might expect that both packed and capillary SFC methods would be competitive and the method of choice depend on the particular separation desired. 

OT columns in CEC are analogous to OT columns in gas chromatography. A significant practical advantage of OT columns, especially compared to packed column CEC, is the ease with which the electrolyte can be flushed through the OT column using a moderate applied pressure. 

The first commercially available packed columns for gas chromatography were those available with the Perkin-Elmer vapor fractometer, Model 154, in 1954. Although the identities of the packings were at first proprietary, they soon became known to the scientific community. At first these columns were simply designated by a capital letter of the alphabet along with a brief description of the type(s) of analytes they could separate. Each column contained 20% liquid phase coated on 60/80-mesh Chromosorb. The columns and their chemical composition are given in Table 2.1. 

In gas chromatography (GC) the sample, which may be a gas or liquid, is injected into a stream of an inert gaseous mobile phase (often called the carrier gas). The sample is carried through a packed or capillary column where the sample s components separate based on their ability to distribute themselves between the mobile and stationary phases. A schematic diagram of a typical gas chromatograph is shown in Figure 12.16. 

A chromatographic column provides a location for physically retaining the stationary phase. The column s construction also influences the amount of sample that can be handled, the efficiency of the separation, the number of analytes that can be easily separated, and the amount of time required for the separation. Both packed and capillary columns are used in gas chromatography. 

The assay of ethyleneamines is usually done by gas chromatography. Compared to packed columns, in which severe tailing is often encountered due to the high polarity of the ethyleneamines, capillary columns provide better component separation and quantification. Typically, amines can be analyzed using fused siUca capillary columns with dimethyl silicones, substituted dimethyl silicones or PEG Compound 20 M as the stationary phase (150). 

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