Distribution mechanism of protonated l,10-phenanthroline between unbuffered aqueous and 1,2-dichloroethane phases

The faradaic ion transfer of protonated l.iO-phenanthroline [H(Phen)+] across the interface between unbuffered aqueous and 1,2-dichloroethane (DCE) solutions was investigated by means of current scan polarography at ascending aqueous electrolyte electrode, as well as chronopotentiometry. It follows from the splitting of the waves observed at the pH of aqueous phase (sodium sulfate solution) between 2.5–3.8 that neutral reagent (Phen) distributes into the aqueous phase, where it is protonated. The positive wave is associated with the mass transfer controlled by the H+influx, whereas the negative one is by the Phen influx. The reverse chronopotentiometry indicated that all the protonated transfer processes were reversible. A good agreement between experimental results and theoretical treatment was achieved. The aqueous acid dissociation constant of protonated Phen, K₂ can be evaluated from the dependence of the wave heights on the pH in the base of the equilibrium.