Partition coefficient

There is an equilibrium between the analyte in the two phases. The more the analyte interacts with the stationary phase, the more it will stay in the column. If it interacts more with the mobile phase, it will stay less time in the column. The partition coefficient (K) is used to relate the concentration of the analyte in each of the two phases, as shown below:

Where K is the Partition coefficient, C_A^{stationary\ phase} is the molar concentration of analyte in the stationary phase and C_A^{mobile\ phase} is the molar concentration of the analyte in the mobile phase. The longer an analyte spends time in the stationary phase, the larger the K value is.