Chemometric Analysis of Voltammetric Data on Metal Ion Binding by Selenocystine

The behavior of selenocystine (SeCyst) alone or in the presence of various metal ions (Bi³⁺, Cd²⁺, Co²⁺, Cu²⁺, Cr³⁺, Ni²⁺, Pb²⁺, and Zn²⁺) was studied using differential pulse voltammetry (DPV) over a wide pH range. Voltammetric data matrices were analyzed using chemometric tools recently developed for nonlinear data: pHfit and Gaussian Peak Adjustment (GPA). Under the experimental conditions tested, no evidence was found for the formation of metal complexes with Bi³⁺, Cu²⁺, Cr³⁺, and Pb²⁺. In contrast, SeCyst formed electroinactive complexes with Co²⁺ and Ni²⁺ and kinetically inert but electroactive complexes with Cd²⁺ and Zn²⁺. Titrations with Cd²⁺, Co²⁺, Ni²⁺, and Zn²⁺ produced data that were reasonably consistent with the formation of stable 1:1 M­(SeCyst) complexes.