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Solubilisation of drugs in micellar systems studied by eluent gel permeation chromatography
M Draper1, M Savage, J H Collett
1Manchester Polymer Centre, University of Manchester, UK.
Purpose:
The purpose of the study was to investigate the potential of a chromatographic method which is based on elution gel chromatography (EGPC) in the study of solubilisation of drugs in micellar solutions.
Methods:
The EGPC method differs from conventional GPC in the use of a solution of the associating surfactant as eluent (rather than solvent) and the injection of a small volume of solution of different concentration (or alternatively injection of solvent alone) to probe the association equilibrium in the eluent. The technique was applied to a study of the solubilisation of selected drugs in aqueous micellar solutions of a triblock copolymer (Synperonic-PE F127) composed of oxyethylene [E, OCH2CH2] and oxypropylene [P, OCH2CH(CH3)] units with nominal molecular formula E98P67E98.
Results:
EGPC curves were obtained showing vacancy peaks at the elution volumes of the drugs, clearly demonstrating their solubilisation. In addition, the micelle-molecule equilibrium of the copolymer surfactant could be monitored at all times. Quantitative determination of the partition of solute between micelles and solvent phase was not possible due to the incomplete conversion of molecules to micelles in solutions of the selected copolymer.
Conclusions:
The EGPC technique provides evidence for the solubilisation of the drugs in aqueous solutions of Synperonic F127; a more thorough assessment of its potential for quantitative measurement of solubilisation requires the use of a surfactant which is wholly (or at least mainly) in the micellar state under the conditions of use.