Binding of Cd 2+ and Zn 2+ with the Phytochelatin (γ‐Glu‐Cys) 4 ‐Gly: A Voltammetric Study Assisted by Multivariate Curve Resolution and Electrospray Ionization Mass Spectrometry

The complexation of Cd 2+ and Zn 2+ with the phytochelatin (γ‐Glu‐Cys) 4 ‐Gly (PC 4 ) is studied by Differential Pulse Polarography (DPP) assisted by Multivariate Curve Resolution with Alternating Least Squares (MCR‐ALS) and by Electrospray Ionization Mass Spectrometry (ESI‐MS). In the case of Zn 2+ , voltammetric results show the presence of an inert electroinactive Zn 2+ PC 4 complex, which is confirmed by ESI‐MS. In the case of Cd 2+ , the unitary DPP peaks and the concentration profiles obtained by MCR‐ALS from DPP titrations of PC 4 with Cd 2+ suggest the formation of two electroactive Cd 2+ PC 4 complexes. The first complex, with a 1 : 1 stoichiometry, shows a fixed DPP peak potential characteristic of a kinetically inert behavior. After further Cd 2+ additions a second labile complex seems to be formed. This behavior is confirmed by ESI‐MS detection of CdPC 4 and Cd 2 PC 4 complexes.