Packing, factors quality

After packing, the quality of the packed bed must be checked. This can be done by injection of a small pulse of salt or a small organic molecule. The number of plates (N) should be determined, as well as the asymmetry factor. The asymmetry factor and the theoretical plates are very sensitive measures of the quality of packing, but once the column is packed, it will not last forever. The packed bed undergoes a change in its structure and at some point, the column will collapse. It is not very easy to predict the time point of collapsing because this is a chaotic process [94]. 

Air permeability is a quality that relates closely to wearer comfort. The authors examine various fabric parameters to develop a statistical model for air permeability. They propose a polynomial model with linear terms of cover factor, fabric thickness, twist factor, and yam packing factor, and quadratic terms of cover factor, fabric thickness, and packing factor ... 

Additional factors influencing column performance are the type and quality of the packing process, which mainly determines the theoretical plate count (N) of the column. In contrast to HPLC columns the efficiency of the separation itself is determined predominantly by the quality of the sorbent alone (pore... 

The peak measured for a plate number determination contains additional information about the packing quality of a column. The same peak may also be used to quantify information about the shape as well. The peak width on both sides of the perpendicular through the peak maximum is measured at a height of 10% of the maximum height (see Fig. 14.2). The quotient of the back by the front part of the peak is defined as the asymmetry factor (AF) ... 

In the elucidation of retention mechanisms, an advantage of using enantiomers as templates is that nonspecific binding, which affects both enantiomers equally, cancels out. Therefore the separation factor (a) uniquely reflects the contribution to binding from the enantioselectively imprinted sites. As an additional comparison the retention on the imprinted phase is compared with the retention on a nonimprinted reference phase. The efficiency of the separations is routinely characterized by estimating a number of theoretical plates (N), a resolution factor (R ) and a peak asymmetry factor (A ) [19]. These quantities are affected by the quality of the packing and mass transfer limitations, as well as of the amount and distribution of the binding sites. 

Asymmetry parameters <5(X) have been obtained for a number of substituents8. Several factors limit the reliability of such derived parameters, e.g. the validity of additivity and other assumptions, the influence of conformation, electronic and steric interactions of substituents, additional strain in polycyclic systems, crystal packing effects and size and quality of the data sample. 

The market has often been seen as one of low-quality products with an overriding convenience factor, but over the last 25 years packaging developments and increasingly affluent consumers have encouraged the development of this market. Early products in the market were packed in pre-formed plastic cups, pouches or early TetraPaks, but today there is a wide variety of packing options available. 

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