System Maps for the Retention of Neutral Compounds on an Electrostatic-Shielded Reversed-Phase Column

The system constants of the solvation parameter model are used to prepare system maps for the retention of small neutral compounds on an octadecylsiloxane-bonded positive shield porous silica stationary phase (Luna Omega PS C18) for aqueous mobile phases containing 10-70% (v/v) methanol or acetonitrile. Electrostatic interactions (cation exchange) for weak bases were observed using acetonitrile-water but not methanol-water mobile phases at a similar level to a sterically shielded octadecylsiloxane-bonded silica column (Kinetex XB-C18). The system constants of the solvation parameter model and retention factor correlation plots for varied compounds indicated that the Luna Omega PS C18 stationary phase was (near) selectivity equivalent to the diisobutyloctadecylsiloxane-bonded superficially porous silica column Kinetex XB-C18. No specific interactions related to the embedded charged/chargeable functional group were observed compared with other high-purity type-B silica octadecylsiloxane-bonded stationary phases for typical reversed-phase separation conditions with unbuffered mobile phases.