Moving phase

Chromatography (Section 13 22) A method for separation and analysis of mixtures based on the different rates at which different compounds are removed from a stationary phase by a moving phase... 

The concentration profiles of the solute in both the mobile and stationary phases are depicted as Gaussian in form. In due course, this assumption will be shown to be the ideal elution curve as predicted by the Plate Theory. Equilibrium occurs between the mobile phase and the stationary phase, when the probability of a solute molecule striking the boundary and entering the stationary phase is the same as the probability of a solute molecule randomly acquiring sufficient kinetic energy to leave the stationary phase and enter the mobile phase. The distribution system is continuously thermodynamically driven toward equilibrium. However, the moving phase will continuously displace the concentration profile of the solute in the mobile phase forward, relative to that in the stationary phase. This displacement, in a grossly... 

Recalling the plate theory, it must be emphasized that (Vm) is not the same as (Vm)-(Vm) is the moving phase and a significant amount of (Vm) will be static (e.g., that contained in the pores). It should also be pointed out that the same applies to the volume of stationary phase, (Vs), which is not the same as (Vs), which may include material that is unavailable to the solute due to exclusion. 

Ki) is the distribution coefficient of the solute between the moving phase and the static pore contents, (Vp(i)),... 

In equation (37), for an incompressible mobile phase, the kinetic dead volume is (Vi(m)) which is the volume of moving phase only. Consequently, at a flow rate of... 

Total Interstitial Volume, value extrapolated from the retention volumes of ions of different size Interstitial Moving Phase Volume... 

Pore Volume Containing Components of the Mobile Phase Having Composition differing from that of the Moving Phase, by difference... 

Dispersion caused by the resistance to mass transfer in the stationary phase is exactly analogous to that in the mobile phase. Solute molecules close to the surface will leave the stationary phase and enter the mobile phase before those that have diffused further into the stationary phase and have a longer distance to diffuse back to the surface. Thus, as those molecules that were close to the surface will be swept along in the moving phase, they will be dispersed from those molecules still diffusing to the surface. The dispersion resulting from the resistance to mass transfer in the stationary phase is depicted in Figure 8. 

The potential governing these electrokinetic effects is clearly at the boundary (the face of shear) between the stationary phase (the fixed double layer) and the moving phase (the solution). This potential is called the electrokinetic potential or the zeta potential. An electrokinetic phenomenon in soil involves coupling between electrical, chemical, and hydraulic gradients. 

The invention also included catalyst immobilization, which was incorporated to facilitate the separation step. Maintaining the catalytic activity while meeting the requirements of the mechanical properties clearly imposes very restrictive conditions on the immobilization support material. Where and how a fixed bed of catalyst is included in a desalting process, or even a moving phase, is not clearly defined. The patent [251] was issued in 1994, and no further development to this scheme has been published since then. 

In column chromatography the mobile (moving) phase is a liquid that carries your material through an adsorbant. I called this phase the eluent, remember Here a gas is used to push, or carry, your vaporized sample, and it s called the mobile phase. 

The term liquid chromatography (LC) is applied to any chromatographic procedure in which the moving phase is liquid, as opposed to gas chromatography (GC) where a gas is utilized as a mobile phase (see discussion in Chapter 14). Classical column chromatography (see Section 15.1), paper chromatography—a forerunner of thin-layer chromatography (see Chapter 13), and HPLC are all examples of LC. This should clarify why it is inappropriate to further abbreviate HPLC to LC unfortunately, it is still commonly done. 

The difference in movement rates of various compounds through a column is attributed to differential migration in HPLC. This can be related to the equilibrium distribution of different compounds such as X, Y, and Z between the stationary phase and the flowing solvent(s), or mobile phase. The speed with which each compound moves through the column (ux) is determined by the number of molecules of that compound in the moving phase, at any moment, since sample molecules do not move through the column while they are in the stationary phase. The molecules of the solvent or mobile phase move at the fastest possible rate except in size exclusion chromatography, where molecular... 

When the fraction of molecules X in the moving phase is zero (M — 0), no migration occurs and ux is zero. If the fraction of molecules X in the moving phase is 1 (i.e., all molecules of X are in the mobile phase, M — 1), then molecules X move through the column at the same rate as solvent molecules and ux = u. As a result, M is also the relative migration rate of compound X. 

A sample calculation for growth of a second phase in a matrix phase (i.e., the growth of ferrite in austenite) would take the following procedure. The flux balance equation at the moving phase interface is formulated as... 

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