Study of the Hg binding with chelation therapy agents by differential pulse voltammetry on rotating Au-disk electrode and electrospray ionization mass-spectrometry

A recently proposed electroanalytical method, using differential pulse voltammetry (DPV) on the rotating Au-disk electrode, and electrospray ionization mass-spectrometry (ESI-MS) has been applied to study the binding of the pharmaceutical chelating agents meso-2,3-dimercaptosuccinic acid (DMSA), sodium 2,3-dimercaptopropanesulfate (DMPS) and d-penicillamine (d-Pen) with Hg²⁺. From the use of voltammetric titrations it was possible to obtain a detailed picture of the complexation processes at concentrations much lower than in previous studies. Predominant species were Hg(Pen)₂, Hg₂(DMSA)₂ and Hg(DMPS)₂. For Pen, Hg(Pen) was also deduced from DPV data, while Hg₂(Pen)₄ from ESI-MS. For DMSA and DMPS, Hg₂L species were detected by DPV, and Hg₂L₃, Hg₃L₃ as well as Hg₂(DMPS)₂ and Hg(DMSA)₂ by ESI-MS. When possible, DPV data were analyzed by multivariate curve resolution with alternating least squares (MCR-ALS).