On the physical meaning of the specific retention volume in gas chromatography

A rigorous derivation of formulas for an integral averaging of the pressure and flow rate of the mobile phase in a chromatographic column is performed in connection with the lack of understanding of the physical meaning of the pressure-gradient correction factor j for the carrier gas and its misuse. It is shown that an averaging of the above values over the column length and the time of residence of the solute leads to three different forms of the factor j. Multiplying of the V-R - V-M value by the j(3)(2) factor corresponds to the recalculation of the retention volume to the pressure (p) over bar averaged over the column length. For equilibrium chromatographic conditions and an ideal gas mobile phase, the specific retention volume is directly proportional to the thermodynamic distribution constant for the partition of the solute between the mobile and stationary phases; as a result, this quantity is independent of the pressure and the gas flow rate in the column.