The equations describing the fluid concentration of the three species in a fixed-bed chromatography column are:

,

where is time, is distance, represents porosity, stands for the effective diffusivity, is the rate of chemical reaction (negative for reactants and positive for products), and the are the solid-phase concentrations that are related to the fluid concentrations via adsorption constants , .

The reaction rate is , and the initial and boundary conditions are: , , , and , , where is the time that species is injected into the chromatograph. Chromatographic separation is based primarily on the difference in adsorptivity , as well as the difference in the diffusion coefficient You can follow the trajectory of the system by varying adsorptivities, diffusion coefficients, fluid velocity, reaction rate, and the time of injection of reactant .