Effect of pressure on solute capacity factor in HPLC using a non-porous stationary phase

The pressure applied in liquid chromatography (LC) can influence the capaci ty factor of analytes. Using commercial equipment, column (33 x 4.6 mm) and 1.5 mu m non-porous, tetradecyl (C-14) coated silica particles, a moderate but significant change in the capacity factor was observed with increasing pressure. Depending on the experimental conditions the relationship was fo und to be either linear or non-linear. In the latter case the retention inc reased at first, but later tended to decrease at still higher pressure. The results direct attention to the role of the pressure (and hence of flow ra te and heat of friction) in determing capacity factors.