Optimization of Efficiency The Kinetic Approach

The internal diameter is inserted in millimeter, and is the total porosity of the interior of the separation column. It is a dimensionless ratio between the volumes occupied by the mobile and stationary phase inside the column and for modern columns packed with spherical, porous stationary phases has a value around 0.7. Another way to calculate u is based on the hold-up time simply by the quotient Llty. This is intuitive as is the time that the nonretained analyte needs to travel the length L of the column. 

We will not need to discuss the factors A, y, and co to a greater extent as they do not vary significantly, cannot be influenced by the user, and are not necessary for understanding the fundamental relationships. It is important to understand the meaning of the diffusion coefficient (or diffusivity) and the stationary phase particle diameter dp. The diffusion coefficient describes the speed of diffusion of the analyte in the mobile phase (in this simplified approach both inside and outside the stationary phase pores). It depends on the molecular properties of the analyte, as well as on the temperature-dependent viscosity of the mobile phase. While the particle diameter is fixed with a given column, the diffusion coefficient can be altered without the need to change the column. It can change with the 

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