Interaction of alkali and alkaline earth ions with Ochratoxin A

► Fluorescence spectroscopy reveals cation-Ochratoxin A (OTA) interactions. ► Alkali ions shift the equilibrium of OTA to formation of a dianionic structure. ► Alkaline earth ions directly bind to OTA in the order: Mg2+, Ca2+, Ba2+. ► Quantum chemical calculations and logK values support our experimental data.