The development and validation of accurate and reliable analytical methods using techniques such as capillary electrophoresis, liquid chromatography, UV-spectrophotometry, spectrofluorimetry and mass spectrometry for separation and determination of some selected drugs in different matrices are presented in the first three chapters. The developed methods were applied to the determination of these compounds in their dosage forms and/or in biological fluids such as human plasma. The stability indicating characteristics including the analysis and separation of certain drugs from their alkaline, acidic, oxidative, thermal or photolytic degradation products along with the study of the degradation kinetics were also investigated. The first chapter focuses on the liquid chromatographic methods and the second chapter covers the capillary electrophoretic methods whereas the third chapter includes the UV-spectrophotometric and spectrofluorimetric methods. On the other hand, the fourth chapter shows how functionalized silica nanoparticles can be used in achieving enhanced electrophoretic separations of selected groups of acidic and basic drugs. Finally, the fifth chapter of this dissertation presents a library of fluorescently labeled-silica nanoparticles that can be used in certain hydrophobicity-based detection applications such as fingerprint detection.