Thermodynamic and voltammetric study on carnosine and ferrocenyl-carnosine.

A potentiometric study on the interactions of L-carnosine (CAR) (2-[(3-aminopropanoyl)amino]-3-(1 H -imidazol-5-yl)propanoic acid) with two toxic metal cations, Hg 2+ and Cd 2+ , is reported here. The elucidation of the metal (M 2+ )-CAR interactions in aqueous solution highlighted the speciation model for each system, the dependence of the formation constants of the complex species on ionic strength (0.15 ≤ I /mol L -1 ≤ 1) and temperature (288.15 ≤ T /K ≤ 310.15) and changes in enthalpy and entropy. The sequestering ability of CAR towards the two metal ions was quantified and compared with that with Pb 2+ , previously determined. Considering the complexing ability of CAR and its unclear electrochemical properties, a more electroactive derivative, the ferrocenyl-carnosine (FcCAR), was synthesized and its complexing ability was evaluated by UV-vis spectroscopy. FcCAR electrochemical properties were investigated by Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV) on Screen-Printed Electrodes (SPEs), to evaluate its sensing properties. Electrochemical responses in the presence of Hg 2+ and Pb 2+ have been shown to be promising for the electrochemical detection of these metal cations in aqueous environment.