Topics - Distribution Coefficient
If a solute is introduced into any two phase system which may be gas/solid, gas/liquid, liquid/liquid or liquid/solid, it will become distributed between the two phases and, when equilibrium is reached, the solute distribution will be defined by the distribution coefficient. The distribution coefficient of a solute between two phases is calculated as the ratio of the concentration of the solute in one phase to the concentration of the solute in the other phase under equilibrium conditions. Either phase may be used as the reference phase, but in chromatography, the distribution coefficient is always referred to the stationary phase (i.e. the ratio of the concentration of the solute in the stationary phase to that in the mobile phase). The concentration may be taken as mass per unit volume in both phases (which is the most usual) or the mass per unit mass in both phases which is sometime employed in gas solid chromatography. The distribution coefficient is temperature dependant.