Column: capacity

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... 

Although the chiral recognition mechanism of these cyclodexttin-based phases is not entirely understood, thermodynamic and column capacity studies indicate that the analytes may interact with the functionalized cyclodextrins by either associating with the outside or mouth of the cyclodextrin, or by forming a more traditional inclusion complex with the cyclodextrin (122). As in the case of the metal-complex chiral stationary phase, configuration assignment is generally not possible in the absence of pure chiral standards. 

The absolute pressure may have a significant effect on the vapor—Hquid equiHbrium. Generally, the lower the absolute pressure the more favorable the equiHbrium. This effect has been discussed for the styrene—ethylbenzene system (30). In a given column, increasing the pressure can increase the column capacity by increasing the capacity parameter (see eqs. 42 and 43). Selection of the economic pressure can be faciHtated by guidelines (89) that take into consideration the pressure effects on capacity and relative volatiHty. Low pressures are required for distillation involving heat-sensitive material. 

Plate-Column Capacity The maximum allowable capacity of a plate for handling gas and liquid flow is of primaiy importance because it fixes the minimum possible diameter of the column. For a constant hquid rate, increasing the gas rate results eventually in excessive entrainment and flooding. At the flood point it is difficult to obtain net downward flow of hquid, and any liquid fed to the column is carried out with the overheaa gas. Furthermore, the column inven-toiy of hquid increases, pressure drop across the column becomes quite large, and control becomes difficult. Rational design caUs for operation at a safe margin below this maximum aUowable condition. 

FIG. 22-12 Pulsed -column capacity versus column size for 65 percent p-xylene feed. To convert gallons per hour to cubic meters per hour, multiply hy 0.9396 to convert square feet to square meters, multiply hy 0.0929. (McKay et al., prepr., 59th nat. meet. AIChE, East Columbus, Ohio.)... 

Many of the above factors that affect column operation are due to vapor flow conditions being either excessive or too low. Vapor flow velocity is dependent on column diameter. Weeping determines the minimum vapor flow required while flooding determines the maximum vapor flow allowed, hence column capacity. Thus, if the column diameter is not sized properly, the column will not perform well. Not only will operational problems occur, the desired separation duties may not be achieved. 

Trace enrichment or preconcentration by LC-LC methods are based on the possibility that the analytes will be retained as a narrow zone on the top of the first column when a large volume of sample is pumped trough the column. Good reproducibility can be achieved when the column capacity is not exceeded and the column is not overloaded. Trace enrichment is usually performed when relatively non-polar... 

Several applications involve the removal of large amounts of triglicerides, including the determination of wax esters in olive oil (39), sterols and other minor components in oils and fats (40, 41), PCBs in fish (42), lactones in food products (43, 44), pesticides (45), and mineral oil products in food (46,47). Grob et al. (47) studied the capacity of silica gel HPLC columns for retaining fats, and concluded that the capacity of such columns is proportional to their size, although the fractions of the volumes that are then transferred to the GC system grow proportionally with the column capacity. For these reasons, 2-3 mm i.d. LC columns are to be preferred for LC-GC applications. 

Reflux Failure (a) At top of distillation column, capacity is total overhead vapor [10], (b) when source of heat is in feed stream, capacity is vapor quantity calculated in immediate feed zone [3], (c) when reboilers supply heat to system, capacity is feed plus reboil vapors [3]. Each situation must be examined carefully. 

Fractionation of Serum and Column Capacity. A Fractionation of human serum on the SW-3000 column is shown in Figure 3. 

Packing gel permeation column. Suspend 50 g of Bio-Beads in the GPC eluting mixture and allow the beads to swell overnight. Pour the suspension all at once into the chromatographic column (capacity ca 180 mL). Once the gel has settled to a height of... 

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. 

The column capacity for any given antibody solution may not be the same and has to be determined empirically for each batch. Therefore, this column eluate and the first two column volumes of wash should be saved, since they may still contain some of the desired antibodies. The titer of the eluate can be tested, or the eluate can be reapplied to the gel at the end of the first purification. 

Breneman, C. M. and Rhem, M. (1997) QSPR Analysis of HPLC column capacity factors for a set of high-energy materials using electronic van der Waals surface property descriptors computed by transferable atom equivalent method. J. Comput. Chem. 18, 182-197. 

Ca detector cell capacity factor/column capacity factor for a given solute... 

In the downstream processing of bioprocesses, fixed-bed adsorbers are used extensively both for the recovery of a target and for the removal of contaminants. Moreover, their performance can be estimated from the breakthrough curve, as stated in Chapter 11. The break time tg is given by Equation 11.13, and the extent of the adsorption capacity of the fixed bed utilized at the break point and loss of adsorbate can be calculated from the break time and the adsorption equilibrium. Affinity chromatography, as weii as some ion-exchange chromatography, are operated as specific adsorption and desorption steps, and the overall performance is affected by the column capacity available at the break point and the total operation time. 

Speed of separation Column capacity Retention factor, k Selectivity factor a Effective plate number, N... 

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