The neat CorA and CorA-ASD formulations were investigated using the biphasic dissolution apparatus BiPHa+ [24 (link)] (Figure 2 ). For this purpose, 50 mL of HCl (0.1 M) were filled in a cylindrical vessel with a diameter of 5 cm and kept at a temperature of 37 °C for the total dissolution. The samples were prepared by weighing out 10 mg neat API or 50 mg ASD formulation. The samples were then added into the vessel. The hydrodynamic effect was achieved by triangle magnetic stirrers. After 30 min (representing the stomach passage), FaSSIF-V2 like concentrate [24 (link)] was added to the aqueous phase simultaneously to the first pH-shift from pH 1.0 to 5.5 (simulating the upper small intestine), and 50 mL of 1-decanol was added automatically above the aqueous phase. After 90 min the next pH-shift from pH 5.5 to 6.8 after 90 min was adjusted gradually (simulating the lower small intestine). Both pH-shifts were caused by adding a respective amount of McIlvaine buffer [24 (link)]. The complete dissolution took 4.5 h. The concentration profiles of both the aqueous and organic phases were measured continuously with an 8454 UV-Vis spectrophotometer (Agilent, Waldbronn, Germany) at 394 nm in the organic phase and in the aqueous phase at 325 nm (pH 1) and 336 nm (pH 5.5–6.8) and quantified via external calibration curves. Three independent dissolution tests were performed for each sample.
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