Volume column, distribution

A summary of the data for the Zorbax column obtained by Alhedai et al. [11] is shown in Table 2. It is seen that the distribution of the various chromatographically important volumes within a column is neither simple nor obvious. It would seem that about 70% of the column volume is occupied by mobile phase but only about 50% of that mobile phase is actually moving. 

In the development of the plate theory and the derivation of the equation for the elution curve of a solute, it was assumed that the initial charge was located In the first plate of the column. In practice, this is difficult to achieve, and any charge will, in fact, occupy a finite column volume and consequently a specific number of the first theoretical plates of the column. Consider the situation depicted in figure 1 where the initial charge is distributed over (r) theoretical plates. 

The distribution of the elements are based on qualitative emission spectrographic analyses of the numbered segments. The Cs and Na distributions are based on quantitative analyses of each segment. Since Cs is concentrated in the leading band, the 137cs DF was dependent on the degree of column loading, i.e., for columns loaded to 50 capacity and washed with one column volume of water,... 

Figure 13.3. Appearance of non-size-exclusion effects on SEC-elution curves of polyelectrolytes and other charged analytes including low-molecular-weight organic acids. Kd is the distribution coefficient and Ve, V0, and Vt are elution volume of the analyte, column void volume, and total column volume, respectively.

Since Vs is difficult to measure, it is common to use an alternative distribution coefficient, called Kav (Equation 3). In this approach, Vs is replaced by the difference between the total column volume (Vt) and the interstitial volume (VD) of the column packed with the chromatographic matrix (Ladisch, 2001 Moraes and Rosa, 2005). 

Determination of Molecular Weight Distribution. A 1.6- X 95-cm column of Sepharose C1-4B in 50% tris(ethylenediamine)cadmium dihydroxide (1 1 with water) was prepared and equilibrated by elution with six column volumes of 50% tris(ethylenediamine)cadmium dihydroxide. Downward flow with a pressure head of 125 cm was used. 

Figure 3-22. Cumulative pore volume distribution of different HPLC columns indicating monomodal pore size distribution for polymer monolith and bimodal distributions for both packed particulate silica and silica monolith columns. (Reprinted from reference 90, with permission.)...

Cylindrical pellets of four industrial and laboratory prepared catalysts with mono- and bidisperse pore structure were tested. Selected pellets have different pore-size distribution with most frequent pore radii (rmax) in the range 8 - 2500 nm. Their textural properties were determined by mercury porosimetry and helium pycnometry (AutoPore III, AccuPyc 1330, Micromeritics, USA). Description, textural properties of catalysts pellets, diameters of (equivalent) spheres, 2R, (with the same volume to geometric surface ratio) and column void fractions, a, (calculated from the column volume and volume of packed pellets) are summarized in Table 1. Cylindrical brass pellets with the same height and diameter as porous catalysts were used as nonporous packing. 

Pilot plant studies (flow rates, 1 cm/s) with the SB-1 anion exchange resin (column diameter, 0.3-0.7 cm) yielded distribution coefficients of the order D = 400 cmVg. The boron sorption process was shown to be film diffusion controlled. The equilibrium values of boron loading were reached in 6-8 hr [280]. Boron elution and resin regeneration were carried out with 0.1 M NaOH. The complete elution of boron required 10 column volumes at 10 BV and yielded concentrates of 100 mg/L. This facilitated the eventual reduction to solid concentrates of alkali metal borates [281]. 

IUPAC recommendations for defining D are [7] distribution coefficient, D the ratio of the total (analytical) amount of a solute per gram of dry ion exchanger to its analytical concentration (total amount per cm ) in the solution concentration distribution ratio, D the ratio of the total (analytical) concentration of a solute in the ion exchanger to its concentration in the external solution (dimensionless) the concentrations are calculated per cm of the swollen ion exchanger and cm of the external solution volume distribution coefficient, D, the ratio of the total (analytical) concentration of a solute in the ion exchanger calculated per cm of the column or bed volume to its concentration (total amount per cm ) in the external solution. 

Factors effecting the peak separation include column volume, particle porosity, pore size distribution and solute conformation. Column dispersion is influenced by column length, particle size and the mobile phase temperature, viscosity and flow rate. 

Fig. 1 Diagram depicting the retention volume, corrected retention volume, dead point, dead volume, and dead time of a chromatogram. Fq total volume passed through the column between the point of injection and the peak maximum of a completely unretained peak F total volume of mobile phase in the column F (a) retention volume of solute A F (a) corrected retention volume of solute A F extra column volume of mobile phase volume of mobile phase, per theoretical plate vy. volume of stationary phase per theoretical plate distribution coefficient of the solute between the two phases n number of theoretical plates in the column Q column flow rate measured at the exit.

A packed column as used in chromatography is a porous medium with a multimodal pore distribution. There are usually two modes in this distribution, but three-mode distributions may also be encormtered, as we see later. In a classical column made by packing the porous particles of an adsorbent, the first mode is made of the interparticle pores, the fraction of the column volume through which the mobile phase flows. The second one is made of the intrapartide pores, within... 

All column chromatographic separations operate on the same principle the distribution of solute between two dissimilar phases—a mobile phase and a stationary phase. In each procedure, sample is introduced into one end of the column and the mobile phase transports the sample components toward the other end of the column. In the absence of interaction with the stationary phase, all components would exit the other end of the column after a time, to, based on the column volume and mobile-phase flow rate and could be detected at the other end of the column using an on-line detector. If an interaction with the stationary phase occurs, the time taken for a solute to elute from the column would be increased by the time that the solute spends in association with the stationary phase (tj ). The ratio of is directly proportional to the distribution coefficient between the stationary phase and the mobile phase and is referred to as the capacity factor (or retention factor) k. The ratio of the k s of two solutes to be separated, where the subscripts denote the second... 

---