Retention in Reversed-Phase Ion-Pair Chromatography of Amines On Alkyl-Bonded Phases

Reversed phase ion-pair chromatography of phenethylamine derivatives (noradrenaline, adrenaline, dopamine, synephrine, tyramine and pholedrine) and lower alkylamines has been performed with octyl sulfate as counter ion in an aqueous eluent with a low content of 1-pentanol. LiChrosorb RP-18 was used as the solid phase. The retention of lithium and potassium in the system has also been studied. On the basis of adsorption and retention studies a model for the chromatographic behaviour of the amines is proposed that includes interaction with two sites with different binding ability in the stationary phase. The adsorption capacity of the sites has been calculated as well as adsorption constants for the octyl sulfate ion pairs.