The work of this research reports the use of different analytical techniques used for the quantitation of analytes like High Performance Liquid Chromatography, Ultra Performance Liquid Chromatography, Divalent ion complex formation, Mass Spectroscopy, Nuclear Magnetic Resonance spectroscopy (NMR) etc. The methods were developed and validated for single, binary, quaternary and five combinations of analytes. The developed methods were validated as per current ICH guidelines to prove the stability-indicating nature and toprove their suitability for the intended purpose. Also the structural elucidation of stressdegradedproducts was achieved by 1HNMR, and LC-MS-MS/MS studies.The fast LC(UPLC) is the preference of the recent scenario which generates the results faster than HPLC and is environmental friendly due to the use of less solvent for analysis. Ultra PerformanceLiquid Chromatography (UPLC) methods for single components Emtriciatbine and Efavirenz were developed successfully and validated as per current ICH guidelines under this thesis. Also UPLC method for determination of eight impurities of Flupirtine Maleate from bulk substance was successfully developed and validated as per ICH.