Stainless steel electrode for simultaneous stripping analysis of Cd(II), Pb(II), Cu(II) and Hg(II)

Traditional electrodes for stripping analysis generally have narrow electrochemical window, require the modification of electrode or the addition of additional ions. To solve these problems, stainless steel has been used as the electrode for electrochemical stripping analysis for the first time. Square wave anodic stripping voltammetry (SWASV) has been used for the detection of Cd²⁺, Pb²⁺, Cu²⁺, and Hg²⁺. Type 304 stainless steel electrode gives well-defined, sharp, and separated stripping peaks for these metal ions. The electrode, best operated at + 0.3 V (Hg²⁺), - 0.05 V (Cu²⁺), - 0.41 V (Pb²⁺), and - 0.7 V (Cd²⁺) and after a 300 s deposition at - 1.0 V, has linear responses in the concentration ranges of 0.075-5 μM for Pb²⁺ and Cu²⁺, 0.5-5 μM for Cd²⁺, and 0.1-5 μM for Hg²⁺. The limits of detection (at S/N = 3) are 0.033 µM for Pb²⁺, 0.0073 µM for Cu²⁺, 0.23 µM for Cd²⁺, and 0.028 µM for Hg²⁺. The reproducibility, expressed as relative standard deviation, is 3.2% for Pb²⁺, 2.6% for Cu²⁺, 5.1% for Cd²⁺, and 2.5% for Hg²⁺ (each 1 μM levels; for n = 6). The electrode was successfully applied to the determination of the ions in spiked groundwater samples. This study shows that stainless steel is a better alternative to mercury electrode for stripping analysis because of its well-defined and sharp stripping peaks, high sensitivity, low background, low toxicity, good reproducibility, and much wider electrochemical window.