QUADRUPOLAR EFFECTS ON THE RETENTION OF AROMATIC-HYDROCARBONS IN NORMAL-PHASE LIQUID-CHROMATOGRAPHY

The retention mechanism of aromatic hydrocarbons in normal phase liqui d chromatography has been investigated with respect to the dominant mo lecular interactions between the polar stationary phase and the solute . The retention behavior of these aromatic solutes is compared with th at of aliphatic hydrocarbons with similar molecular polarizability, an d the difference between them is interpreted in terms of relative cont ributions of dispersion, induction and electrostatic interactions to t he observed retention. While the aliphatic hydrocarbons are unretained in all of the chromatographic systems studied, the aromatic hydrocarb ons show increasing retention with their molecular quadrupole moments. This is consistent with a retention model in which the electrostatic interactions that involve a solute quadrupole moment play a major role in controlling the retention of aromatic hydrocarbons in normal phase liquid chromatography.