Plate Theory and Extensions - Temperature Changes During the Passage of a Solute Through a Theoretical Plate in Gas Chromatography > Page 82

  (vlrlSl+vsrsSs)dq = Heat Evolved in Plate (HC) in Time (dt).

          - Heat Conducted Radially from Plate (GC) in Time (dt)    (67)

Now, the solute is distributed largely over 4 plates in the column and thus, as (n) is large, the differential temperature between plates is negligible, and so the heat conducted axially along the column will be very small compared with that conducted radially to the walls and from the system.

The change in concentration in the mobile phase (gas) during the passage of a volume (dv) will be,


Thus, the change in concentration in the liquid phase during the passage of a volume of mobile phase (dv) will be


Consequently the heat evolved in plate (n) (HC) will be given by


where (h) is the heat of solution of the solute in the liquid phase, given in appropriate units.

The heat conducted from the plate (GC) in time (dt) will be given by