High-performance liquid chromatographic study of the interactions between immobilized beta-cyclodextrin polymers and hydrophobically end-capped polyethylene glycols

The formation of inclusion complexes between polyethylene glycols (PEGs) be aring hydrophobic ends (naphtyl and phenyladamantyl) and beta -cyclodextrin polymers (poly beta -CD) immobilized onto silica particles was studied by high-performance liquid chromatography (HPLC). It was shown that hydrophobi c interactions were involved in the retention mechanism of these compounds, since retention volumes decreased when organic solvents were added to the mobile phase while it was the contrary in the presence of salts. Moreover, the association could be reversed by adding a competitor (hydroxypropyl bet a -cyclodextrin) to the mobile phase. A theoretical model permitted the eva luation of affinity constants of 1:1 complexes formed between the modified PEGs and the immobilized poly beta -CD which depended on the type of hydrop hobic groups grafted to the PEG. (C) 2001 Elsevier Science B.V. All rights reserved.