HPLC–MS experiments were performed on a U-3000 system (Dionex, Voisins-Le Bretonneux, France) coupled to an Exactive mass spectrometer equipped with an H-ESI ion source (Thermo Scientific, Courtaboeuf, France). The mass spectrometerwas operated in positive ion mode. Spray voltage was set at 4.5 kV. The capillary temperature was set at 250 ◦C. Tube lens and skimmer voltages were set at 50 and 20 V, respectively. Nitrogen was used as sheath, auxiliary and sweep cone gas at flow rate of 15, 2 and 1 (arbitrary units), respectively. Heater temperature was set at 200 ◦C.