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-imidazol-5-yl)propanoic acid) with two toxic metal cations, Hg and Cd, is reported here. The elucidation of the metal (M)-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 ≤ /mol L ≤ 1) and temperature (288.15 ≤ /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, 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 and Pb have been shown to be promising for the electrochemical detection of these metal cations in aqueous environment.