Stationary-phase volume

The total stationary-phase volume required to process a given feed stream is proportional to the inlet concentration and volume of the feed. For example, for a typical inlet concentration of protein of 10 g/L, in a 100 L volume of feed, a column volume of at least 100 L is needed for size-exclusion chromatography. In comparison, an ion-exchange column having an adsorption capacity of 50 g/L would only require 20 L of column volume for the same feed. 

To increase Vs, the chromatographer can increase the surface area of the stationary phase materials in normal-phase liquid chromatography, increase the stationary phase volume in reversed-phase or partition liquid chromatography, or increase the ion-exchange capacity in ion-exchange liquid chromatography. In general, if the internal diameter of a column is constant, the retention time... 

Entropy changes were estimated with Eq. 4 assuming that V, is equal to the total stationary phase volume existing in the column. Therefore, these values reflect more properly the relative differences in entreaties of transfer instead of the standard molar entropies that would require to use the volume of the active stationary phase. 

In the GPC experiment, polymer molecules are separated by size or their hydro-dynamic volume because of their ability to penetrate part of the pores volume of the gel particles, i.e., the stationary phase. As the sample moves along the column with the mobile phase, the largest molecules are almost entirely excluded from the pores of the stationary phase, whereas the smallest find almost all the stationary phase accessible. The smaller the molecule, the more of the stationary phase volume is accessible to it and the longer it stays in that phase. Consequently, small molecules are eluted from the column later (Fig. 18.1). 

Stationary phase volume. VS(VL). Total volume of stationary phase liquid on the support material in partition columns. 

Kp may be related to the retention volume, the mobile phase volume, and the stationary phase volume. The total moles of substance injected onto the column, n, is divided between the stationary phase and the mobile phase,... 

For the assessment of the extent of change of the phase ratio of a HPLC column system with temperature or another experimental condition, several different experimental approaches can be employed. Classical volumetric or gravimetric methods have proved to be unsuitable for the measurement of the values of the stationary phase volume Vs or mobile phase volume Vm, and thus the phase ratio ( = Vs/Vm). The tracer pulse method266,267 with isotopically labeled solutes as probes represents a convenient experimental procedure to determine Vs and V0, where V0 is the thermodynamic dead volume of the column packed with a defined chromatographic sorbent. The value of Vm can be the calculated in the usual manner from the expression Vm = Eo — Vs. In addition, the true value of Vm can be independently measured using an analyte that is not adsorbed to the sorbent and resides exclusively in the mobile phase. As a further independent measure, the extent of change of 4> with T can be assessed with weakly interacting neutral or... 

If we disengage ourselves from the consideration of mobile and stationary phases and assume (as a very rough approximation) that column void volume is the volume of the mobile phase = Yo) and leave stationary-phase volume... 

Figure 2-12 represents the temperature dependencies of a homologous series of alkylbenzenes retention at 60% MeCN/40% water on a Phe-noemenex Luna-C18 column. The intercepts for each analyte is different from others, which essentially means that each analyte requires the determination of its own stationary phase volume. 

The ratio of the stationary-phase volume. K, and the mobile-phase volume, V is termed the phase ratio, F (Eq. (7.26)). 

Second, one of the phases (stationary one) must be retained in the rotating column to a required extent. The most important factor, which determines the separation efficiency and peak resolution for both organic and inorganic compounds, is the ratio of the stationary-phase volume retained in a column to the total col-... 

K is the partition coefficient, and e is the ratio of the stationary phase volume to the gas phase volume. 

A gel-filtration column prepared using Bio-Gel P-100 had a void volume of 5.0 mL and a stationary-phase volume of 50.0 mL. The column was calibrated using six proteins of known molecular weight, by measuring the elution volume of each peak (Table. 14.7). An unknown protein was then applied to the column, and its elution volume was measured. Given the data in the table below, determine the molecular weight of the unknown protein. 

It is obvious from Fig. 1 that the chromatographic separation of components in a mixture is dependent on two factors the difference in retention times of two adjacent peaks, or more precisely, the difference between peak maxima and the peak widths. It was shown in the preceding discussion that the retention of a solute is a thermodynamic process controlled by the distribution coefficient and the stationary-phase volume. The peak width, or band broadening, on the other hand, is a function of the kinetics of the system. 

According to Ito, "CCC is governed by the same equations that apply to all forms of chromatography but, because the phase volumes are known in CCC, it is simple to express the equations in terms of the partition coefficient K = C/C where C represents solute concentration in the stationary phase, s, and mobile, m, phases, rather than the capacity factor k = K(V/VJ, where F represents the volume of the stationary, s, and mobile, m, phases. Because there is no supporting matrix, and the column volume, F (column) is known, the stationary phase volume can be obtained from... 

The volume of a chromatographic column consists of the stationary-phase volume and the void volume, the volume occupied by the mobile phase. The latter can be determined from and the flow rate. One void volume of the mobile phase is required to flush the column once. 

Phase ratio, /3 is used in GC to describe the thickness of the stationary phase, measured as the ratio of stationary phase volume. Kg, to mobile phase volume. Km- Thicker stationary phase films give higher capacity factors and therefore longer retention times ... 

Stationary-phase volume l-s Packing preparation data... 

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