Plate Theory and Extensions - The Column Dead Volume > Page 29

If the column volume is (Vc) and contains a volume of mobile phase (VM), a volume of stationary phase (VS) and a volume of support (e.g., silica) (VSi), then,

 

                                 Vc = VM + VS + VSi                               (27)

 

             Now,                   VM Vm

(Vm) is the moving phase and a significant amount of (VM) will be static (e.g., contained in the pores). The same applies to the volume of stationary phase, (VS), which is not the same as (VS), as it may include material that is unavailable to the solute due to exclusion.

Now, the volume of a cylindrical column will be given by

      

                                          Vc = pr2l                                     (28)

                                where (r) is the column radius,

                                   and  (l) is the column length.

Hence,                        VM+ VS + VSi = pr2l                             (29)

The individual volumes, (VM), (VS) and (VSi), can now be apportioned according to their chromatographic pertinence.