Microelectrodes for the determination of heavy metal traces in physiological conditions. Hg, Cu and Zn ions in synthetic saliva RID C-8787-2011

The present article reports an introductory study aimed to define voltammetric methodologies employing microelectrodes for the quantitative evaluation of Hg and other heavy metals in physiological-like matrices as synthetic saliva. The utilization of graphite, Pt and Au microdisc electrodes as voltammetric sensors in the differential-pulse stripping analysis of Hg, Cu, Ag, Sn and Zn (the main constituents of the well-known dental or silver amalgams, largely used for the dental restoration) has been studied in different artificial saliva. The best analytical performances, in terms of detection limit, repeatability and width of the potential window available, have been shown by graphite electrodes. Co-deposition effects (e.g., Pb or Cd) play an important role in improving detection limit and repeatability of the responses of graphite electrodes in the determination of Hg. The conditions for contemporary determination of Hg, Cu and Zn in a single re-oxidation step are also established and selected experimental conditions are proposed by virtue of the absence of Cu-Zn intermetallic interference in the deposition step. On the other hand, the study has shown that no possible combination of experimental conditions, i.e., nature of electrode and saliva, presence or absence of other reducible ions, allows the detection of Ag and Sn at μg dm−3 levels.