4.3.3. LC–ESI–MS/MS Analysis
Phenolic compounds’ metabolites were identified using a Prominence Liquid Chromatograph (Shimadzu, Japan) coupled to an ion trap Esquires-LC mass spectrometer (Bruker Daltonics, Billerica, MA, USA) with an electrospray ionization (ESI) interface. The chromatography condition was the same as that used for metabolite quantification by HPLC-DAD. After passing through the DAD detector, the flow rate was changed to 0.2 mL/min to inject the samples into the mass spectrometer. ESI was left in the positive mode for anthocyanins and in the negative mode for the other compounds. The mass spectrometer condition was collision energy of 4500 and 4000 V for the positive and negative modes, respectively, and capillary temperature of 275 °C. Scanning 