Electrochemical Detection Of Chromium (Ⅵ) And Mercury (Ⅱ) By Chemically Modified Electrode

With the enhancement of the people’s environmental awareness and the growing demand of living standard improvement,the presence of trace heavy metals in the natural and living environment,and the implications for public health are widely recognized in recent years.Heavy metals have great hazard to human even in trace quantities.The measurement of heavy metal ions is one of the foundation and key steps in heavy metal pollution prevention and treatment.Comparedwithchromatographicanalysisandspectroscopicanalysis,electrochemical methods are favored by more and more researchers because of their high sensitivity,relative simplicity.And electrochemical methods are easy to realize on-line monitoring and capable for portable equipment applications.However,Chromium and Mercury are relatively difficult to detect due to their low environmental capacity in many pollution sources.In this paper,trace amount of chromium（VI）was measured by cathodic adsorption stripping voltammetry on the polyaniline/phosphorus tungsten heteropoly acid/graphene modified electrode.Experiment on the determination of trace mercury（II）by pyridinemethanol ruthenium carbonyl complex/gold nanoparticles modified electrode was carried out.The main contents are as follows.1.A polyaniline/phosphorus tungsten heteropoly acid/graphene modified glassy carbon electrode was prepared by a one-step electropolymerization method.The prepared electrode was used to the determination of chromium（VI）by Differential pulse cathodic stripping voltammetry.Cr（VI）reduces at the surface of the electrode to Cr（III）,which forms immediately a complex with PW₁₂O₄^3-present in excess on the electrode surface due to its adsorption.The Cr（III）-PW₁₂O₄ complex is reduced further to Cr（II）complex during a cathodic scan,a sensitive reduction peak can be produced.There is a good linear relationship between the reduction peak current and the concentration of Chromium（VI）.2.Nano-gold modified electrode was prepared by cyclic voltammetry,potentiostatic and chronocoulometry electrodeposition.The surface morphology of nano-gold modified electrode was characterized by scanning electron microscopy（SEM）.The effects of various condition in the preparation of gold modified electrode were discussed in order to determine the optimized preparation method.Then,the ruthenium carbonyl complex-nanogold modified electrode was prepared by the drop coating method.The result shows that the measured oxidation peak current has a linear relationship with the Hg（II）concentration.3.The pyridinemethanol ruthenium carbonyl complex and AuNPs modified glassy carbon electrode was prepared by chronocoulometry one-step electrodeposition.The influence of the conditions such as ruthenium carbonyl complex concentration,chloroauric acid concentration and enrichment potential,enrichment time on the determination of mercury（II）has been discussed.Different concentrations of mercury（II）were determined under the optimized experimental conditions.The standard curve with relative less standard deviation is obtained.Our results are informative to the development of on-line automatic monitor and portable equipment for the measurement of heavy metal ions.