Solubility of CIP.HCl in Nanoemulsion

The solubility of CIP.HCl was determined in nanoemulsion components as follows: OA and IPM as oil phases; TW-20 and Labrasol^® as surfactants; PG, PEG 400, and ethanol as cosurfactants; and 5% acetic acid and water as aqueous phases, as described in [49 (link)]. Briefly, an excess amount of CIP.HCl was dissolved in 3 mL of tested samples placed in 10 mL screwed-on test tubes. Samples were mixed using a vortex mixer and placed in a water bath at 37 °C for 24 h. Then samples were centrifuged at 3500× g for 15 min (Hermle Z326K centrifuge, Wehingen, Germany), and the supernatants were appropriately diluted with 0.1 N HCl. The concentration of CIP.HCl was assessed by UV-Vis spectrophotometry (Varian, Cary UV/Vis spectrophotometer) at a wavelength (λ_max) of 277 nm, using a standard calibration curve of CIP.HCl prepared in 0.1 N HCl.