Investigation of binary polar solvent mixtures, solubilized ferroelectric salts and Paraffin-based derivatives using dielectric spectroscopy

Abstract

Water properties are the subject of investigations in physics, chemistry, biology and different applied fields of natural science. Liquid dosage forms, generally based on aqueous solutions, take an important role in drug administration e.g. as parenteral preparations, ophthalmic formulations or as oral solutions for children and elderly patients. Sufficient drug solubility in water is a prerequisite for orally administrated solid dosage forms such as tablets, capsules, etc. to show a sufficient bioavailability. The solubility of a drug is determined by intermolecular forces. While these can be reasonably well characterized in gaseous and solid material, no satisfying description has yet been found for liquid systems, especially for nonideal solutions. The presence of several types of intermolecular interactions let water show rather a complex associated structure due to which it has a number of its abnormal properties. In part A of this work, the intermolecular forces in pure solvents and binary mixtures at 298.2 K (25°C) are investigated, using quasistatic low-frequency and AC highfrequency broadband (0.2-20 GHz) dielectric spectroscopy. The data were interpreted using for the low frequency measurements the modified Clausius-Mossotti-Debye equation according to Leuenberger and Kirkwood-Frohlich equation. For the description of the dielectric relaxation in the high frequency range there are different models available which describe the relaxation behaviour of a polar liquid. The most simple equation is the Debye equation, which will be described and will be compared with the other models in the theory chapter. It has to be kept in mind that the resulting relaxation times (