Measurement of desorption rates from octadecylsilyl bonded-phase HPLC particles and its characterization in terms of pore, surface, and film diffusion.

An instrument is developed to measure rates of desorption of solutes from particulate HPLC packing materials for processes that are quantitatively complete in a few tenths of a second. The instrument is a modified, pressure-driven, stopped-flow device. The major modifications include positioning a very short (0.

Continuous desorption rate measurement from a shallow-bed of poly(styrene-divinylbenzene) particles with correction for experimental artifacts.

A 0.50 mm high bed, containing ca. 3 mg of the nominally non-porous poly(styrene-divinylbenzene) (PS-DVB) sorbent Hamilton PRP-infinity, is located in a valve.

Stationary-phase contribution of 1-propanol organic modifier to changes in sorption of 1-hexanol on an ODS-bonded phase.

Using the reversed-phase bonded-phase HPLC packing Partisil-10 ODS-3, sorption isotherms have been measured for the alcohols 1-propanol (PrOH) and 1-hexanol (HexOH), and as well, a simultaneous sorption curve for the two alcohols has been measured from solutions containing a low and constant concentration of HexOH as sample with increasing concentrations of PrOH as organic modifier. The mobile-phase effect of PrOH is quantified by solution-phase activity coefficients obtained either from vapor/solution equilibrium measurements or from cloud point measurements. Since sorbed alcohols are located at the ODS/solution interface, the stationary-phase effect of PrOH is modeled in terms of three processes: (i) competition for space; (ii) decrease of space required per mole with increasing concentration of sorbed PrOH; and (iii) change of free energy of sorption with increasing concentration of sorbed PrOH.

Chain Unfolding in an ODS-Bonded Phase Caused by the Sorbed Tetra-n-butylammonium Ion.

The simultaneous sorption of the tetra-n-butylammonium ion (TBA(+)) and butanol on the bonded phase sorbent Partisil-10 ODS-3 from an aqueous mobile phase, at the two different ionic strengths 0.50 and 0.050 mol/L, is studied by the column equilibration technique.

Effect of Stationary-Phase Sorption of Organic Modifier from a Water-Rich Mobile Phase on Solute Retention by an ODS Bonded Phase.

Sorption isotherms for 1-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.