Separation of steroid compounds by overloaded preparative chromatography with precipitation in the fluid phase

In order to gain a commercially acceptable yield compared to the adsorption capacity of the column, a rather large amount of sample is separated with preparative chromatography. During the competitive adsorption of the sample-components, the species adsorbing better can force the rest out of the adsorbent phase. As a consequence, the concentrations of the later components may increase in the fluid phase to a level that those species start to precipitate. A mathematical model which takes the precipitation and dissolution into consideration is presented in this paper. Data calculated by this model are compared to that we obtained by using a previous mathematical model as well as the experimental results gained by a laboratory scale separation of steroid compounds on an organic polymer adsorbent. The equilibrium adsorption-desorption and equilibrium precipitation-dissolution is the first approximation of the complicated process mentioned above. In our next publication we are to extend the model with kinetic terms belonging to adsorption-desorption and precipitation-dissolution process respectively.