Question

what to do if the retention volume is less than the mobile phase volume

Answer 1

If volumes are used, the volume of the mobile phase that it takes to elute a peak off of the column is referred to as the retention volume (V_R) and the amount of mobile phase that it takes to elute a non-retained component is referred to as the void volume (V_M). A solute’s retention time or retention volume in chromatography is directly related to the strength of the solute’s interaction with the mobile and stationary phases. Retention on a given column pertain to the particulars of that system: - size of the column & - flow rate of the mobile phase.

Capacity factor (k’): k’ = (V_R –V_M)/V_M

k’ is directly related to the strength of the interaction between a solute with the stationary and mobile phases.

k’ = K_D x [Volume_{stationary phase} / Volume_{mobile phase}], as K_D increases, interaction of the solute with the stationary phase becomes more favorable and the solute’s retention (k’) increases. Where K_D = equilibrium constant for the distribution of solute between the mobile phase and stationary phase.

Change the length and size of stationary phase either smaller or bigger as per t_R, so that K_D will increase.

Hope this helped you!

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