PHE concentration in the solution was determined using highperformance
liquid chromatography (Dionex, USA) with a UV
detector at 250 nm. The analytical column contained Acclaim® 120,
C18 5m120 ˚A (4.6mm×150mm) and the mobile phase was 85%
(v/v) acetonitrile and 15% (v/v) deionized water at a flow rate of
1.5 mL/min.