Integrating between (P_i) and (P_o)

                                                               (25)

Substituting for (P_r) in equation (24) from equation (25),

                            =   V_r(o)              

Thus, the correction factor for retention data in GC is .

This factor must be used in all retention volume measurements in GC. It should be noted that the factor depends on the packing being homogeneous and the flow impedance being constant along the column. From the inverse relationship , equation (23) can be used to show how the mobile phase velocity changes along a column for different inlet/outlet pressure ratios.