Stochastic−Dispersive Theory of Chromatography

The stochastic model of chromatography has been combined with mobile-phase dispersion. With the combined model, both the effect of slow mass transfer or adsorption-desorption kinetics and dispersion on the band profile can be characterized. The stochastic model of chromatography is addressed with the characteristic function method. The moments of the peaks are calculated analytically for homogeneous and heterogeneous surfaces. It is shown that even in cases when the characteristic function cannot be calculated in closed form, the moments of the peak, and therefore the retention time, the number of theoretical plates, the peak asymmetry, can be calculated with simple expressions. Therefore, a full description of the chromatographic peak is available for homogeneous and any heterogeneous surfaces provided that the distribution of the sorption energies is known.