Chromatography solute movement

Since membrane pore surface and the chromatography packing surface are both made out of the same polymer material, identical interfaclal forces have to govern both membrane transport and chromatography equilibrium. The only difference between the two systems is that in the latter case, there is no effect of solute movement (kinetic effect) on the retention volume data, and therefore the interfaclal force governing the chromatography equilibrium may be represented only by surface potential working on the solute, which may be expressed by a Lennard-Jones type equation. 

FIGURE 14.1-2 Solute movement solution Tor three component linear chromatography (a) solute movement diagram and (b) predicted product concentrations. 

FIGURE 14.4-2 Solute movement solution Tor four-component feed using column arrangement shown in Figure 14.4-1 A.1 Reprinted with permission from P. C. Wankal, Large-Scale Adsorption and Chromatography, CRC Press, Boca Raton, FL. 1986. 

Application of Linear Solute Movement Theoiy to Purge Cycles and Elution Chromatography... 

Exanqile 18-2. Linear solute movement analysis of elution chromatography... 

Figure 18-6. Results for Exanyle 18-2 for elution chromatography (A) solute movement...

There is an analogy that may be useful in understanding this solute movement analysis. The problems are similar to algebra problems where two trains start to leave a station at the same time, but with different velocities (u and Ug in chromatography). You want to calculate when each train arrives at a second station (a distance L away) and when the tail end of each train (analogous to the feed time, tp) leaves the second station. 

Explain the meaning of each term in the development of the solute movement equations and use this theory for both linear and nonlinear isotherms to predict the oudet concentration and temperature profiles for a variety of different operations including elution chromatography, adsorption with thermal regeneration, PSA, SMB, and ion exchange... 

The equations for rate of solute movement can be derived rigotously, - but a phyncal aigumoit is used here. In all types of chromatography, die solute distributes between the statkmaiy diase and the mobile phase. When solute is in the stationary phase, its velocity with respect to the solid is zero, while when the solute is in the mobile phase, it has the same relative velocity as the moving fluid. Thus, we can calculate die solute velocity ftom the ftaction of time the solute spmids in the mobile phase... 

TAetection of the highly potent impurity, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), necessitated an environmental assessment of the impact of this contaminate. Information was rapidly needed on movement, persistence, and plant uptake to determine whether low concentrations reaching plants, soils, and water posed any threat to man and his environment. Because of the extreme toxicity of TCDD, utmost precautions were taken to reduce or minimize the risk of exposure to laboratory personnel. Synthesis of uniformly labeled C-TCDD by Muelder and Shadoff (I) greatly facilitated TCDD detection in soil and plant experiments. For unlabeled experiments it seemed wise to use only small quantities of diluted solutions in situations where decontamination was feasible and to rely on the sensitivity afforded by electron capture gas chromatography... 

Figure 3.2 Three major methods in chromatography. The commonest form of chromatography involves the introduction of a small volume of sample onto a column and is known as zonal chromatography. Movement down the column is effected by the mobile phase, which may be simply a solvent (A) allowing partition of the test molecules between the stationary and mobile phases. Alternatively, the mobile phase may be a solvent containing solute molecules (B), which actively displace test molecules from the stationary phase. A less frequently used method known as frontal separation (C) does not involve a separate mobile phase but a large volume of the sample is allowed to pass through the column and as the various components separate, concentration fronts develop and their movement can be monitored.

---