Adsorption Isotherms of Hydrophobic Substances onto a Chromatographic Organic Monolith

Abstract

Adsorption isotherms of hydrophobic substances (methylparaben, coumarin, vanillin, isovanillin, and caffeine) onto a chromatographic organic monolith were measured at 24℃. Adsorption isotherms of coumarin and caffeine were linear and were expressed by the Henry equation. On the other hand, the isotherms of methylparaben, vanillin, and isovanillin were non-linear and could be expressed by combining the Henr y and Langmuir equations. Among the adsorbates having almost the same molecular masses, vanillin was adsorbed the most on the organic monolith, and methylparabene followed. The adsorbate hydrophobicity was not a main parameter reflecting the adsorbability, but any specific interaction between the adsorbate and the monolith would play an important role on the absorbability onto the monolith.