# Capillary Chromatography - Capillary Column Theory 5

Consequently, the contribution from the resistance to mass transfer in the stationary phase, for all practical purposes, can be ignored. The resistance to Mass Transfer Ratio for a larger column is shown in figure 16.

It is seen from figure 16 that the larger diameter column exhibits an even grater resistance to mass transfer ratio and at a (k') of unity the resistance to mass transfer in the stationary phase contributes to less than 2% of the total resistance to mass transfer and at practical exit velocities (*i.e.*, 20-30 cm/sec) the fraction is reduced to less than 1.5 %

Column Length 15 m Column Diameter 300 mm

**Figure 16. Graph of Resistance to Mass Transfer Ratio against Mobile Phase Exit Velocity.**

It is clear, that for all practical purposes the resistance to mass transfer in the stationary phase can be ignored and equation (2) can be reduced to,