Column capacity, reduced

Hold-up of column. The hold-up of liquid should be reduced to a minimum compatible with scrubbing effectiveness and an adequate column capacity. The ratio of charge of the still to the hold-up of the... 

As packing factor, F, becomes larger by selection of smaller sized packing gas capacity for the column is reduced and pressure drop will increase for a fixed gas flow. 

Ultra-high flow on capillary columns (0.180 mm i.d.) versus narrow bore (1 mm i.d.) permits to reduce the sample-handling time and to improve column capacity and robustness [14], Moreover, these columns are able to work with sub-2 pm particles, which offer very fast methods to determine the chemical-physical properties of NCE. 

This discussion on the MISPE column capacity shows that it is not easy to define in a scientific manner the capacity of MISPE cartridges. Most published protocols apply the samples as large volumes and then employ a different solvent for the wash. Sample matrix components may also affect retention. Therefore we believe it is more practical to study the capacity for the full protocol and with real samples. If under these conditions the analyte(s) are fully retained, the capacity is sufficient and one may even try to reduce the MIP quantity used. 

Dry-packed beds have higher pressure drops than wet-packed beds. Billet (56) and Kister (40) report cases where changing from dry to wet packing increased column capacity by 5 percent and reduced pressure drop by 10 percent. Ludwig (63) reports cases where this pressure drop reduction was 50 to 60 percent. The... 

Extraction of Am(III) on a POX.11 column this is the main step of the treatment. Before introduction into the POX.11 column, the solution is adjusted to 0.1 to 0.15 M H+ and 0.16 M EDTA. This EDTA concentration corresponds to that of the Fe(III) present. This adjustment is the critical step of the process, as a deficiency of EDTA in relation to Fe(III) results in co-extraction of Fe and Am in the column, thereby reducing capacity of the solvent for americium. Excess EDTA results in the presence of insoluble... 

EBMax is a liquid phase ethylbenzene process that uses Mobil s proprietary MCM-22 zeolite as the catalyst. This process was first commercialized at the Chiba Styrene Monomer Co. in Chiba, Japan in 1995 (16-18). The MCM-22-based catalyst is very stable. Cycle lengths in excess of three years have been achieved commercially. The MCM-22 zeolite catalyst is more monoalkylate selective than large pore zeolites including zeolites beta and Y. This allows the process to use low feed ratios of benzene to ethylene. Typical benzene to ethylene ratios are in the range of 3 to 5. The lower benzene to ethylene ratios reduce the benzene circulation rate which, in turn, improves the efficiency and reduces the throughput of the benzene recovery column. Because the process operates with a reduced benzene circulation rate, plant capacity can be improved without adding distillation capacity. This is an important consideration, since distillation column capacity is a bottleneck in most ethylbenzene process units. The EBMax process operates at low temperatures, and therefore the level of xylenes in the ethylbenzene product is very low, typically less than 10 ppm. 

The operating conditions needed for adsorption rate measurements differ considerably from the requirements of the preparative packed bed operation mode. Kinetic mass transfer effects will increase as the flow rate is increased and the column capacity decreased. Furthermore, the major problem is to differentiate between a diffusion rate-limited process and the kinetic-limited one. The contribution of the diffusional mass transfer to the overall adsorption process will be reduced by using an immunoadsorbent with a low density of binding sites immobilized on a nonporous support. 

If the solvent is nonvolatile, it can cause accumulation of heavy impurities in an extraction loop that are surface-active. Even in trace concentrations, these culprits can have a devastating effect on extractor performance. They can reduce the coalescing rates of drops—and thus reduce column capacity. Since most flooding models are based on pure-component tests, these models tend to be overly optimistic. Relative to a clean system, the presence of impurities can lower column capacity by 20% or more and efficiency by as much as 60%. 

To debottleneck the system, reflux in the rectification column is reduced, giving more overhead product, but with a higher water content. The pervaporation unit is sized to remove enough water that the subsequent entrainer column is also unloaded. Both columns can then realize a significant capacity increase. 

Particular attention has been paid to separation of common anions (see Table 6.1) because they are present in so many types of samples. Complete resolution of common anions may take approximately 20 min (Dionex AS9HC, 9.0 mM sodium carbonate), but the use of a column of lower exchange capacity or the use of a 2.0 mm i.d. column can reduce the separation time to approximately 10 min or less. For high throughput of simple, well-characterized samples, use of a column with unusually low exchange capacity will give a good separation of seven common anions in a approximately 2 min (Fig. 6.5). 

The first example show the separation of enantiomeric amides on a chiral stationary phase (4(a)) and on the same phase but in its liquid-crystalline state (4(b)) (first discovered by Lochmllller and Souter (5)). The enhanced selectivity of the latter is so great that a separation which required about 35,000 plates on a capillary column is reduced to a 100 plate packed column experiment. As a result the practical capacity is increased fom the picogram to the milligram range. 

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