Distribution Constant:

In chromatography, the distribution equilibrium is often simple and is described by the equations that involve the transfer of an analyte between the mobile and stationary phase. Thus, for the solute X, we may write

X_mobile      ⇔ X_stationary

The equilibrium constant, K, for the reaction is known as distribution constant and is given by the following expression

 K = C _S/ C _M .

Where, C_S is the molar concentration of the solute in the stationary phase and C_M is its molar concentration in the mobile phase. Ideally, C_S is straight proportional to C_M over a huge range of concentration. If such a condition exists, a chromatography is known as linear chromatography and results in symmetric Gaussian type peaks. The retention times are independent of the amount of the compound injected. Ideal behaviour, on the other hand, is not attainable in any actual chromatographic process. It is actually non-ideal behaviour which operates and the corresponding chromatography is known as non-linear chromatography.