Ratio, capacity phase

Column Type Length m Internal Diameter mm Film Thickness /tm Phase Ratio Capacity Factor lU mm opi cm/s Column Plate Count Plates Per Meter... 

The separation on the ODS-SDS column is achieved by the addition of a suitable complexing ligand to the mobile phase to discriminate between the various metal ions. The selectivity between two metal ions is achieved through two competing equilibria, namely the complexation equilibrium of the free metal ion in the micellar pseudo-phase and the complexation equilibrium of the metal ion adsorbed on the SDS mono-layer and this is shown in Fig. 1. It is evident from this equilibrium that the distribution ratio (capacity factor) of the metal ion is given by Eq. (1), where the subscripts a and represent the concentration of the free metal ion in the bulk aqueous phase and the adsorbed monolayer, respectively ... 

PharmPrint descriptors substructure descriptors ( pharmacophore-based descriptors) phase capacity ratio = capacity factor —> chromatographic descriptors... 

Dg remains constant over a wide range of resin to liquid ratios. In a relatively short time, by simple equilibration of small known amounts of resin and solution followed by analysis of the phases, the distribution of solutes may be followed under many different sets of experimental conditions. Variables requiring investigation include the capacity and percent cross-linkage of resin, the type of resin itself, the temperature, and the concentration and pH of electrolyte in the equilibrating solution. 

The working capacity of a sorbent depends on fluid concentrations and temperatures. Graphical depiction of soration equilibrium for single component adsorption or binary ion exchange (monovariance) is usually in the form of isotherms [n = /i,(cd or at constant T] or isosteres = pi(T) at constant /ij. Representative forms are shown in Fig. I6-I. An important dimensionless group dependent on adsorption equihbrium is the partition ratio (see Eq. 16-125), which is a measure of the relative affinities of the sorbea and fluid phases for solute. 

An eluted solute was originally identified from its corrected retention volume which was calculated from its corrected retention time. It follows that the accuracy of the measurement depended on the measurement and constancy of the mobile phase flow rate. To eliminate the errors involved in flow rate measurement, particularly for mobile phases that were compressible, the capacity ratio of a solute (k ) was introduced. The capacity ratio of a solute is defined as the ratio of its distribution coefficient to the phase ratio (a) of the column, where... 

As already mentioned, there are two so called "dead volumes" that are important in both theoretical studies and practical chromatographic measurements, namely, the kinetic dead volume and the thermodynamic dead volume. The kinetic dead volume is used to calculate linear mobUe phase velocities and capacity ratios in studies of peak variance. The thermodynamic dead volume is relevant in the collection of retention data and, in particular, data for constructing vant Hoff curves. 

The silica dispersion showed the smallest retention volume. It should be noted, however, that the authors reported that the silica dispersion required sonicating for 5 hours before the silica was sufficiently dispersed to be used as "pseudo-solute". The retention volume of the silica dispersion gave the value of the kinetic dead volume, /.e., the volume of the moving portion of the mobile phase. It is clear that the difference between the retention volume of sodium nitroprusside and that of the silica dispersion is very small, and so the sodium nitroprusside can be used to measure the kinetic dead volume of a packed column. From such data, the mean kinetic linear velocity and the kinetic capacity ratio can be calculated for use with the Van Deemter equation [12] or the Golay equation [13]. 

The explicit form of those equations that satisfy the preliminary data criteria, must then be tested against a series of data sets that have been obtained from different chromatographic systems. As an example, such systems might involve columns packed with different size particles, employed mobile phases or solutes having different but known physical properties such as diffusivity or capacity ratios (k"). 

The choice of variables remaining with the operator, as stated before, is restricted and is usually confined to the selection of the phase system. Preliminary experiments must be carried out to identify the best phase system to be used for the particular analysis under consideration. The best phase system will be that which provides the greatest separation ratio for the critical pair of solutes and, at the same time, ensures a minimum value for the capacity factor of the last eluted solute. Unfortunately, at this time, theories that predict the optimum solvent system that will effect a particular separation are largely empirical and those that are available can be very approximate, to say the least. Nevertheless, there are commercially available experimental routines that help in the selection of the best phase system for LC analyses, the results from which can be evaluated by supporting computer software. The program may then suggest further routines based on the initial results and, by an iterative procedure, eventually provides an optimum phase system as defined by the computer software. 

Capacity Ratio (first eluted peak of the Critical Pair) (k ) Capacity Ratio (first eluted peak of the Critical Pair) (k") Viscosity of the Mobile Phase (r])... 

It is also clear from equation (2) that the sample mass can also be extended by increasing the capacity ratio (k ) of the eluted solutes (i.e, by careful phase selection). In this case the maximum load will increase linearly with the value of (k ) but so will... 

HETP of a TLC plate is taken as the ratio of the distance traveled by the spot to the plate efficiency. The same three processes cause spot dispersion in TLC as do cause band dispersion in GC and LC. Namely, they are multipath dispersion, longitudinal diffusion and resistance to mass transfer between the two phases. Due to the aforementioned solvent frontal analysis, however, neither the capacity ratio, the solute diffusivity or the solvent velocity are constant throughout the elution of the solute along the plate and thus the conventional dispersion equations used in GC and LC have no pertinence to the thin layer plate. 

A suspension containing 50 % solids is to be filtered in a filter press, achieving a concentrated cake of 40 % water (on a weight basis). The filter capacity for the cake is G, = 700 kg/hr. Determine the amount of suspension, the filtrate and the ratio x . The density of the solid phase is 1,600 kg/m and that of the liquid phase is 900 kg/m ... 

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