Stationary–mobile phase distribution coefficient for polystyrene standards

Abstract

The measured shifts of the retention volume V _R of polystyrene (PS) towards lower values in benzene–methanol (Bz–MeOH), and towards higher values in butanone–heptane (But–Hep) are in agreement with our theoretical model, in which both MeOH and But are adsorbed on Lichrospher. This paved way for us to model the chromatographic stationary (s)-phase as MeOH and the mobile (m)-phase as Bz–MeOH, and to calculate the distribution coefficients for PS. For But–Hep, the s-phase has been modeled as But, and the m-phase as But–Hep. A linear relation for the experimental equilibrium distribution P _sm of PS is shown between the s- and m- phases in Bz–MeOH and But–Hep vs. the logarithm of the molecular mass The s- and m-phases for PS in Bz–MeOH and But–Hep are modeled, and is calculated. The results indicate the preference of PS for Bz–MeOH and But. The calculations predict a V _R shift of PS towards lower values in Bz–MeOH, and towards greater values in But–Hep. The different adsorptions on Lichrospher of MeOH (multilayer) and But (monolayer) affect the magnitude of the V _R shift.

Keywords:

• Distribution coefficient
• High performance liquid chromatography–size-exclusion chromatography
• Ternary polymeric system
• Transient stationary phase
• Polystyrene

Acknowledgments

The authors acknowledge financial support of the Dirección General de Enseñanza Superior of the Spanish MEC, Projects PB97-1383 and PM98-0856.