Nonideal chromatography

It is these two points of view which are used in the Chapter 2 to discuss the theory of gas chromatography. Linear, nonideal chromatography may be visualized by the relationships shown in Figures 1.12 and 1.13. 

Figure 1.16. Nonlinear nonideal chromatography. tQ = start of separation (point of sample injection) tR = retention time of component A tg = retention time of component B tn = time of emergence of mobile...

The general case of nordinear, nonideal chromatography has only numerical solutions, and optimization must be carried out using munerical solutions of mathematical models to simulate the performance of SMB and to search for the flow rates and switching times that give the desired separation. This approach is faster and more effective than proceeding by trial and error but, in addition to other parameters, the mass transfer parameters are needed to estimate the operating parameters [19-21]... 

Similarly, a decision must be made whether or not to take into account the influence on band profiles of such phenomena as axial dispersion (dispersion in the direction of the concentration gradient in the column) and resistance to mass transfer (i.e.. the fact that equilibration between mobile and stationary phases is not instantaneous). These phenomena are responsible for the finite efficiency of actual columns. Neglecting them and assuming the column to have infinite efficiency leads to a model of ideal chromatography. Taking them into account results in one of the models of nonideal chromatography. 

Using these two sets of conditions, we can then describe four chromatographic systems (a) linear ideal chromatography, (b) linear nonideal chromatography, (c) nonlinear ideal chromatography, and (d) nonlinear nonideal chromatography. 

FIGURE 2.13 Isotherms for linear nonideal chromatography Cs = concentration at snr-face or in stationary phase Cq = concentration in solution (mobile phase) at equilibrium. 

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