Comparison of laser nephelometric and HPLC techniques for efficient determination of solubility of ibuprofen and its 2-hydroxypropyl-p-cyclodextrin inclusion complex

ABSTRACT Poor drug solubility is a major problem that hinders the discovery and development of new drugs. There is a need for rapid and inexpensive techniques for acquiring reliable drug solubility data. In this study, the suitability of laser nephelometry for the determination of solubility was investigated using ibuprofen, as a model drug of low solubility, and its 2-hydroxypropyl-p-cyclodextrin inclusion complex (ic). This investigation involved the preparation of ibuprofen-ic-cyclodextrin (1:1) using coprecipitation and characterisation. Thermal analysis and assessment of molecular vibrations confirmed the existence of the inclusion complex. The shake flask testing method was employed and carried out in acidic and alkaline media, and solubility data were verified against high-performance liquid chromatography (HPLC). Results obtained via nephelometry showed relative enhanced solubility of ibuprofen in both acidic (0.565 mg ml-1) and basic (7.5 mg ml-1) media, respectively, which was enabled via inclusion complex formation. Relative to nephelometry data, HPLC results showed a similar trend with increased solubility values in acidic (0.454 mg ml-1) and basic (201.73 mg ml-1) media, respectively. The application of laser nephelometry proved to be a quick and relatively cost-effective technique for solubility measurements of the parent drug and its carrier system. Keywords: cyclodextrin, ibuprofen, inclusion complex, laser nephelometry, solubility