MEDIATED ADSORPTION OF DRUG MOLECULES ONTO SOLID-SURFACES AND THE PREDICTION THEREOF BY A CHROMATOGRAPHIC TECHNIQUE

As an example coadsorption data for a series of 4-hydroxybenzoic acid alkyl esters with POE-9.4-nonylphenol were presented. The mediated adsorption is shown to be increased by increasing the alkyl residue of the 4-hydroxybenzoic acid ester. The amount of drug which was coadsorbed was found to be up to 75% of the total drug content when propyl 4-hydroxybenzoate was used as a model compound. For the prediction of such interaction phenomena the use of a liquid chromatographic technique was proposed. This methodology is based on the so called pseudo phase liquid chromatography (PLC). The results obtained by the ''dynamic'' PLC method were in good agreement with the corresponding data from ''static'' equilibrium adsorption experiments. On this basis a prediction was made for several other drug molecules. In addition the use of an equilibrium expression approach according to Arunyanart and Cline-Love permitted calculation of micelle-solute equilibrium constants from capacity factors derived from PLC.