A research group from the University of Lisbon (Lisbon, Portugal) studied the use of stir-bar sorptive extraction (SBSE) with polyurethane and polydimethylsiloxane polymeric phases and high performance liquid chromatography with diode-array detection for the analysis of six acidic pharmaceutical compounds in environmental water matrices such as river, sea, and wastewater samples. The compounds of interest were o-acetylsalicylic acid, ibuprofen, diclofenac sodium, naproxen, mefenamic acid, and gemfibrozil. In this study, the polyurethane phase was found to be more effective at extracting the analytes from the water matrices.