1290 lc system

A shift in the UV spectrum occurred during the release of fenofibrate-loaded MMC, so UPLC-MS was used to determine the origin of the shift. Two samples were weighed into Eppendorf tubes, one with 8 mg fenofibrate-loaded MMC and the other with 0.7 mg crystalline fenofibrate and 7.2 mg MMC. Two milliliters of Milli-Q water was added to the tubes, which were then placed on a plate shaker at 37 °C for 24 h. The supernatants were recovered by centrifugation at 37 °C for 15 min at 23,000×g (Heraeus Megafuge 8R, ThermoScientific) and analyzed by obtaining a full MS spectrum (QTRAP 6500, AB Sciex). A stock solution of fenofibrate dissolved in DMSO was used as reference. Separation was performed on an Agilent 1290 LC-system, with a Waters BEH C18 2.1 × 50 mm (1.7 μm) column, and the run was made in positive mode. The mobile phase consisted of (A) 5% acetonitrile, 0.1% formic acid, and 94.9% Milli-Q water; and (B) 95% acetonitrile, 0.1% formic acid, and 4.9% Milli-Q water. A constant flow rate of 0.5 mL/ min was used for the gradient elution as follows: A was constant at 99% for 1.0 min, then decreased linearly to 20% for 7.30 min. A was thereafter decreased to 10% for 0.2 min, kept constant for 0.5 min, and then increased to 99% for 0.5 min.