Electrochemical Detection Of Arsenic (?) And Chromium (?) On Graphene Modified Electrode

The heavy metal pollution problems in water,soil,food and medicine have been attracted much attention in recent years.The measurement of heavy metal ions is one of the basic and key steps in heavy metal pollution prevention and treatment.Electrochemical methods have important advantages such as high sensitivity,low detection limit,relative simplicity,low cost of equipment,capacity to multi-element determination,and automatic on-line and portable options for the determination of metals at trace levels,compared with the traditional methods in laboratory.It is well known that the mercury-film electrode and hanging mercury drop electrode have played a major role in the development and wide application of electrochemical method.Thus,the development of electrochemical sensors with less toxicity than mercury is still a very promising area.Today,with the development of nanoscience and nanotechnology,nanoparticles such as graphene and CNTs are of great interest due to their important properties such as their unique structure,large surface area,special shape and composition-dependent physical and chemical properties and their numerous possible applications.In this paper,trace amount of arsenic???was measured by cyclic voltammetry on the graphene modified cobalt film electrode;The Cathedic Stripping Voltammetry method for the determination of chromium???with graphene modified bismuth film electrode with KNO₃ as sensitivity enhancer was studied;Experiment on the determination of trace Cr???by SiW₁₂ heteropoly acid modified graphene electrode was carried out.The main contents are as follows.1.Graphene modified cobalt film electrode was prepared and the surface morphology of graphene modified cobalt film was characterized by scanning electron microscopy?SEM?.The results showed that the graphene modified cobalt film electrode has a good catalytic performance for the oxidation of arsenic???,resulting in sensitive peaks of arsenic?III?.There was a good linear relationship between the oxidation peak current and the concentration of As???.The stability and reproducibility of the electrode are excellent.2.The bismuth film has been fabricated on a graphene doped glassy carbon electrode for the determination of chromium???based on the catalytic effect of Cr???-DTPA-NO₃-system.The deposited products on the electrode surface were characterized bySEM and EDS.The corresponding Adsorption Catalytic Stripping Voltammetry reaction mechanism has been discussed.Cr?VI?reduces at the surface of the electrode to Cr?III?,which forms immediately a complex with DTPA present in excess on the electrode surface due to its adsorption.The Cr?III?–DTPA complex is reduced further to Cr?II?–DTPA during a cathodic scan,and a sensitive reduction peak is given.The re-oxidation of Cr?II?to Cr?III?can be initiated by nitrate,producing a parallel chemical?CE?catalytic effect on the reduction.The linear range of chromium???is 1×10-8¹×10-7mol/L.The test results are satisfactory with potential application value.3.The PW₁₂ heteropoly acid modified graphene electrode was prepared.The influence of the conditions such as sweep speed,scanning turns and enrichment potential on the determination of chromium???was discussed.Different concentrations of chromium???were determined under the optimized experimental conditions.The standard curve with arelative less standard deviation is obtained.Our results will provide the theoretical basis for the preparation of chromium sensor based on a heteropoly acid modified graphene electrode.