To decrease the consumption of expensive active pharmaceutical ingredients (APIs) during the determination of their solubility limits by traditional classical methods, which are used in most of quality control laboratories over the world, an instrumental method has been developed based on the UV spectrophotometry. This study was focused on two types of pharmaceutical compounds. First, glatiramer acetate (GLA), also known as copaxone that is currently used to treat multiple sclerosis, has been studied as a water-soluble drug. Second, bortezomib (BZB), also known as velcade, which is an antineoplastic agent used for treatment of mantle cell lymphoma (cancer of the lymph nodes), as an organic-solvent (methanol) soluble drug. The results obtained by the proposed method are discussed and validated according to the solubility limits defined according to USP. Different batches of drugs were used to confirm that the results are reliable. Determination of the solubility of samples with unknown concentrations by using the constructed calibration curves showed that the solubility limit of GLA in water and BZB in methanol is defined as SOLUBLE and SPARINGLY SOLUBLE, respectively, which agrees with results of the traditional method.
