Effect of stationary-phase sorption of organic modifier from a water-rich mobile phase on solute retention by an ODS bonded phase

摘要

Sorption isotherms for l-butanol (BuOH) and eucalyptol (Eu) on Partisil 10 ODS-3 are plotted as concentration sorbed versus activity in aqueous solution. The former follows the Langmuir equation and the latter follows the equation for an "associative bilayer isotherm. with limited solubility in the aqueous phase". Two series of simultaneous sorption experiments of BuOH and Eu were also performed. One series involved measuring the influence of BuOH, as an organic modifier solvent in water, on the sorption of Eu as solute. In the second series, the roles of BuOH and Eu were reversed. These studies show that when sorption is treated as partitioning between two bulk liquid phases, the stationary phase behaves as an ideal solution which is composed of C-18 chains, sorbed organic modifier, and sorbed solute. Combined with the Langmuir isotherm behavior of BuOH, this ideal solution behavior supports the view that BuOH is sorbed at the stationary-phase/mobile-phase interface, with its hydrocarbon tail in the stationary phase. [References: 45]