Chromatography, unified equation

The second approach integrates both the catalytic activity and separation efficiency by dissolving the catalyst in the stationary phase or immobilizing the catalyst on to the stationary phase and using columns that are uniformly coated with the catalytically active stationary phase over the complete capillary length (cf. Figure 21.2b). In this case, elution profiles are obtained that are characterized by plateau formation or a more complex convolution of reactant and product. Today, reaction rate constants can be easily determined with the unified equation of chromatography (see below) [37, 38]. 

Another even more powerful approach is the application ofthe unified equation of chromatography, which allows determining the reaction rate constants of any first-order reaction directly from chromatographic elution profiles without the need for performing reaction progress analysis. This dramatically accelerates the evaluation of temperature-dependent kinetics, as the analysis time no longer Hm-its the rate of measurements. Detailed kinetic data and activation parameters are of great importance to model and predict activities and selectivities by computational methods. 

The unified equation of chromatography (Equations 21.7a and 21.7b) allows the direct calculation of reaction rate constants and and Gibbs activation energies AG for all types of first-order reactions taking place in chromatographic or electrophoretic systems, regardless of the initial concentrations of the reactants A and B and the equihbrium constant... 

The point of all this is simply that we must not use the apparent plate height or the apparent plate number as performance criteria in the unified chromatography techniques on the justification that they already work well for LC and that they work well for GC when a pressure correction is applied. A considerable expansion of theory and an effective means for evaluating equations (7.4) or (7.5) are required first. Likewise, as we consider multidimensional chromatography involving techniques existing between the extremes of LC and GC, we must not build judgments of the multidimensional system on unsound measures of the individual techniques involved. 

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