*2.1. Materials*

All the chemicals employed were reagen<sup>t</sup> grade or higher in quality. HNT, FeCl3·6H2O, FeSO4·7H2O, Fe(NO3)3·9H2O, ammonia solution (NH3 H2O), sodium acetate (CH3COONa), ethylene glycol (C2H6O2), ethanol (EtOH), glucose (C6H12 O6), and OFL were purchased from Merck (Milano, Italy).

High-performance liquid chromatography (HPLC) gradient-grade acetonitrile (ACN) was purchased by VWR International (Milano, Italy), H3PO4 (85% *w*/*w*), and water for liquid chromatography/mass spectrometry (LC/MS) by Carlo Erba Reagents (Cornaredo, Milano, Italy).
