Packings performance characteristics

Occasionally, samples are run that adsorb onto the packing material. Generally, if one of the performance characteristics of the column changes by 10% or more, it is prudent to clean the column. These performance characteristics are (1) asymmetry factor, retention time, resolution, and theoretical plates. 

The distributor and packing are the heart of the performance of this equipment. Their proper selection entails an understanding of packing operational characteristics and the effect on performance of the points of significant physical difference between the various types. 

Relative Performance Characteristics of Tower Packing and Column Trays ... 

Unger, K.K. (editor)(1979). Silica columns packing procedure and performance characteristics. Porous Silica Journal of Chromatography Library, Volume 16. Elsevier, Amsterdam. pp.169 186. 

Lin S H, Peng C F (1997) Performance characteristics of a packed-bed ozone contactor. Journal Environmental Science and Health, A32 929-941. 

The characteristics considered most desirable for good packing performance are a high surface area, a uniform distribution of liquid, and a low resistance to gas flow. 

Sulzer Bros. Ltd., Performance Characteristics, Suiter Column Packing Mellapak, Winterthur. Switzerland. 1985. 

Recently, 530-p.m capillaries, sometimes called megabore columns, have appeared on the market. These columns will tolerate sample sizes that are similar to those for packed columns. The performance characteristics of megabore open tubular columns are not as good as those of smaller diameter columns but are significantly better than those of packed columns. 

Table 31-4 compares the performance characteristics of fused-silica capillary columns with other types of wall-coated columns as well as with support-coated and packed columns. 

The solutions are transferred to the reaction kettle through metered tubes, and the precipitated lead azide is washed and either filtered and dried or packed wet for shipment. In some countries the practice is to introduce the azide into detonators or explosive trains only at the place of manufacture in other countries, notably the U.S.A., transportation is permitted, and the packed azide may be stored and used in detonators or fuze trains at distant locations. However, while such peripheral practices and associated equipment are important, it is the control exercised during the metathesis in the kettle that affects the product and, more importantly, introduces subtle differences that make one form of lead azide different from another in performance characteristics, if not in gross physical appearance. Therefore, the emphasis of the present discussion will be on the reaction kettles and their associated equipment, and the following section will emphasize the control on the metathesis. 

An overview of capillary gas chromatography is presented. Selected environmental applications, such as PCB s in water, PAH s in airborne particulate matter, and TCDD s at the part-per-trillion level illustrate the separation and analysis of complex mixtures. The chromatographic performance, characteristics, and trade-offs of packed and capillary columns are described in terms of permeability and efficiency, sample capacity, choice of stationary phase, high temperature capabilities, quantitative accuracy, and the development of GC separation methods. 

Figures 29-.3 and 29-4 compare Ihe performance characteristics of a packed column when elution is performed with supercritical carbon dioxide and a conventional liquid mobile phase. Figure 29 3 shows that at a linear mobile-phase velocity of 0.6 cm/s. the supercritical column yields a plate height of 0.013 mm whereas...

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