| Stripping analysis has been widely recognized as a powerful tool for trace metal analysis. Mercury-based electrodes have been traditionally employed for achieving high reproducibility and sensitivity of the stripping technique. However, because of the toxicity of mercury, new alternative electrode materials are highly desired. There were several reports suggesting the replacement of mercury with some other materials. But none of them approached the favorable electrochemical behavior of mercury. In recent years, Joseph Wang et al first introduced the bismuth film electrodes for anodic stripping voltammetry (ASV) and adsorptive stripping voltammetry (AdSV) measurement of heavy metals. These bismuth film electrodes can offer high sensitivity, renewable surface and reproducible, and bismuth is 'environmentally-friendly', with a low toxicity and a widespread pharmaceutical use. So it has been proposed as a possible alternative to mercury. Based on the mechanism of bismuth film electrode, a new electrode material was proposed. Because the position of stannum and bismuth is catercorner in element periodic table, stannum may have analogical character of bismuth. The following experiments proved stannum film electrode also had favorable electrochemical measurements for some trace metals. Based on the attractive and unique behavior of the bismuth film electrodes, we have developed some new film electrodes. In addition, the applications of stannum film electrode have been researched.The main research works are as follows:1. Bismuth/poly(aniline) film electrode and its applicationA novel voltammetric method using a bismuth/poly(aniline) film electrode has been developed for simultaneous measurement of Pb(II) and Cd(II) at lowμg l-1 concentration levels by anodic stripping voltammetry. We discussed the polymeric conditions of poly(aniline), the mechanism of the bismuth microparticles and the renewable process of this new electrode. The results confirmed that the bismuth/poly(aniline) film electrode offered high-quality stripping performance compared with the bismuth film electrode. Well-defined sharp stripping peaks were observed for Pb(II) and Cd(II), along with an extremely low baseline. The presence of the poly(aniline) film enhanced the activity of bismuth microparticle on the GC electrode for determining these metals. The bismuth/poly (aniline) electrode has been applied to the determination of Pb(II) and Cd(II) in tap water sample with satisfactory results.2. Electrochemical determination of tin by using the bismuth film electrodeThe bismuth film electrode (BiFE), in combination with differential pulse anodic stripping voltammetry, was proposed for the determination of low concentrations of tin in non-deoxygenated solutions. The new protocol is based on simultaneous in situ formation of the bismuth film electrode on a glassy carbon electrode, together with electrochemical deposition of tin, followed by an anodic stripping scan. Several experiential parameters were optimized, such as concentration of bismuth ions, deposition potential, deposition time and pH of the model solution. BiFE exhibited highly linear behavior in the examined concentration range from 0.4 to 5 mg l-1of Sn(II) (r = 0.998) with the detection limit of 0.15 mg l-1 Sn(II). The results show that bismuth can form 'fusible' alloys with stannum and it explored the scope and power of the bismuth film electrode.3. Electrochemical behavior of stannum film electrode and its applicationThe stannum film electrode was generated in situ by depositing simultaneously the stannum film and the metal cations by reduction on a glassy carbon electrode. Then, the reduced products were oxidized using differential pulse anodic stripping voltammetry (DPASV). Experiments conducted under identical conditions indicate that the stripping voltammetric performance of the stannum film electrode (SFE) compares favorable with that of BFE and the stannum was cheaper than bismuth. The voltammetric behavior of Cr(III), Cd(II) and Zn(II) at the stannum film electrode was studied by DPASV. This film electrode exhibited a high sensitivity. So this new electrode was used for the simultaneous determination of trace levels of chromium(III) and cadmium(II). In a pH 5.3 acetate buffer, the linear ranges of Cr(III) and Cd(II) determined are both from 10.0 - 110.0μg l-1, with the detection limit of 2.0μg l-1 for Cr(III) and 1.1μg l-1 for Cd(II). Finally, the stannum film electrode was applied to the analysis of cadmium in tap water. In addition, the analytical application of the SFE for the measurement of zinc using DPASV was developed. This new electrode exhibited good linear behavior in the examined concentration range from 10.0-90.0μg l-1 of zinc (r = 0.998), with the detection limit of 3.5μg l-1 Zn(II) and good precision.4. Study on the electrochemical behaviors of the stannum/bismuth film electrode and its applicationA procedure for the simultaneous determination of zinc and cadmium on the stannum/bismuth film electrode by differential pulse anodic stripping voltammetry has been developed. This new stannum/bismuth film electrode is prepared by adding Sn(II) and Bi(III) directly to the sample solution and simultaneously depositing the stannum and the bismuth and target meals on the glassy carbon substrate. Numerous key experimental variables have been characterized and optimized especially studying the proper proportion between Sn(II) and Bi(III).This stannum/bismuth film electrode displays an attractive stripping voltammetric performance which compares favorably with that of common bismuth-film electrode. In a pH 4.7 acetate buffer, the linear calibration graphs for Zn(II) and Cd(II) in the range from 2.0 to 80.0μg l-1 were obtained, with the detection limit of 0.18μg l-1 for Zn(II) and 1.16μg l-1 for Cd(II). Finally, the stannum/bismuth film electrode was successfully applied to the determination of Zn in tap water with satisfactory results.
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