The number of new drugs introduced into the market is increasing day by day. These drugs may be either new entities or partial structural modification of the existing one. Very often there is a time lag from the date of introduction of a drug into the market to the date of its inclusion in pharmacopoeias. This happens because of the possible uncertainties in the continuous and wider usage of these drugs, reports of new toxicities (resulting in their withdrawal from the market), development of patient resistance and introduction of better drugs by competitors. Under these conditions, standards and analytical procedures for these drugs may not be available in the pharmacopoeias. It becomes necessary, therefore to develop newer analytical methods for such drugs. Using QbD, pharmaceutical quality is assured by understanding and controlling formulation and manufacturing variables, degradation products and related impurities in bulk drugs, pharmaceutical formulations and biological samples such as whole blood, plasma, serum and urine. Instances of these include estimation of Raloxifene through the HPLC method with UV detector , florescence detector , diode array detector , photodiode array detector , UPLC-ESIQ-MS , UPLC–MS-MS , LC–MS-MS method , etc.