*2.6. Aqeous Media Solubility Studies*

The equilibrium solubility of FEN in 0.0125 M SLS, FaSSGF, and FaSSIF was determined by the addition of excess FEN to 1 mL of media in 1.5 mL centrifuge tubes. The tubes were vortexed for 10–20 s to aid drug dissolution and placed on a rotator in the oven at 37 ◦C. After 48 h, samples were centrifuged at 44,800 rcf for 30 min at 37 ◦C to precipitate any undissolved drug. Methanol was used to extract dissolved drug from the supernatant, prior to dilution with mobile phase and quantification of FEN content by HPLC.
