Effect of pressure on retention factors in HPLC using a non-porous stationary phase

Pressure and temperature have significant influence on retention in HPLC. This study investigates the effect of pressure and temperature on the retention behavior of aromatic hydrocarbons (toluene, ethyl benzene, butyl benzene, pentyl benzene) and polar, acidic and basic samples (phenol, acetophenone, N,N-dimethyl aniline, benzophenone) on a reversed phase column. The effect has been studied on non-porous,tetradecyl (C-14) coated silica particles. We found that the adsorption-induced decrease of the partial molar volume of the solutes investigated was between DeltaV(m) = 5 - 15 cm 3 mol(-1). The increment of the decrease of the partial molar volume due to the addition of one CH2 group, for the homologous series of the aromatic hydrocarbons is approximately DeltaV(CH2) = 2.3 cm(3) mol(-1).