Regular packed columns

The constant Bo characterises the permeability of the column, which depends on the interstitial porosity of the column, c, (with regularly packed columns, e, is usually close to 0.40) and increases with the second power of the mean particle diameter, dp. From the Koz.eny-Carman equation [16.171 it follows ... 

The ordered structure of the regular packings column with uniform flow canals allows a precise phase distribution and small loss of pressure [50] (Fig. 2.52). The very large... 

In a regular packed column (a column in which the ratio of column diameter, dc, to particle diameter, dp, is greater than 10), K° is given by the equation ... 

We will now try to understand different device configurations for continuous chromatographic separation. Consider a regular packed column with a sample of a multicomponent feed injected at z = 0, the mobile phase moving with an interstitial fluid velocity and equilibrium... 

Samples of the reaction products were withdrawn out of the reactor at regular time intervals and analysed Dy gas chromatography. The conditions for the GC measurements were as follows a packed column (4m- 1/8") with 0V 210 10 % + XE 60 5 % on Chromosorb WHP 80/100 and column temperature isothermal at 110°C - Dodecane was used as a standard. 

The use of nonporous supports for protein immobilization will eliminate the problems associated with the intraparticle diffusion limitations. With columns regularly packed with small spherical particles of limited size distribution, the mass transfer effects associated with a nonuniform flow distribution will be minimized. Extra column effects due to diffusion in the stagnant liquid pockets will be reduced by using short and properly designed connecting lines to the injector and the detector. 

The contributions due to the mass transfer at the particle boundary will be decreased 49] with monodisperse spherical particles of small diameter (1-2 //m). However, with very small particles a regular packing of the columns is difficult to achieve. Moreover, the corresponding increase of the column capacity will lead to a decrease of the contribution for the binding rate process Eq. (14)]. A compromise is thus necessary between these two contradictory requirements. Experiments by varying particle size are needed to ascertain the validity of adsorption rate measurements at the gas-liquid interface. 

When considering a packed bed the interparticle or interstitial porosity amounts to approximately 40%. The average diameter of these interstitial voids calculates for a fairly regular packing to 0.4 times of the particle diameter, e.g. a regularly packed bed with 15 p,m particle creates interstitial pores of 6 pm. A bimodal particle size distribution of silicas employed for preparative columns can often be found, e.g. a major distribution around 15 pm and a minor peak at 4 pm. These small particles are thought to occupy the interstices between the 15 pm diameter particles and thus to stabilize the bed. 

Dry packing is another very efficient way to pack a column. It is most often used in conjunction with regular or bonded silica gel. If done well, a dry packed column will give excellent resolution. As the name implies, dry packing... 

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