The Research Of Determination Of Pb(Ⅱ)and Cd(Ⅱ)using A Electrochemical Sensor Based On Nitrogen-doped Carbon Ball

Lead(lead, Pb) and Cadmium(cadmium, Cd) are a kind of apoisonous and harmful heavy metals, they can destroy the normal physiological function of human after entering the human body, therefore, how to detect the heavy metal quickly and efficiently has a reality significance. Electrochemical test of heavy metals was recognized as a kind of rapid detection methods of heavy metals, especially suitable for on-line monitoring. In electrochemical detection, the introduction of modified materials can be improve the performance of the electrode surface very well to achieve the goal of improve detection results. The mainstream of the electrochemical research direction is introducing a modified material preparation by modifying the bare electrode electrochemical sensor.Platinum doping porous carbon(Pt-C) and nitrogen doped carbon ball(N-Cs) are a kind of novel material, reported so far, most of the literature are the preparation and characterization of two materials, there are rarely reported for the actual detection, especially for the report about heavy metal detection. This thesis will using these two materials to prepare of the electrochemical sensors, glass carbon electrode(GCE) as working electrode.It can be make four different preparation of electrochemical sensors according to the dispersing agent and the way of modification. Respectively, Pt–C prepared with chitosan modified GCE sensor(CTS/Pt-C/GCE),Pt-C prepared with chitosan modified GCE and besmear Nafion membrane sensor(CTS/Pt-C/Nafion/GCE), N-Cs prepared with deionized water modified GCE sensor(N-Cs/GCE) and N-Cs prepared with chitosan modified GCE sensor(CTS/N-Cs/GCE). Make a detection of lead based on this four sensors. According to the results, choose the N-Cs/GCE sensor as detection sensor. Ac impedance electrochemical characterization also showed that N-Cs/GCE has a lower surface resistance compared with GCE. The results of detection of Pb2+ show that it has a good linear relationship between 1×10-8mol/L to 4×10-6mol/L, the limit detection(S/N=3) of lead is 1.04×10-9 mol/L.It is also using this kind of sensor in detection of Cd2+, Optimize the experimental parameters and under the optimal conditions for experiments. The results show that it has a good linear relationship between 1×10-7mol/L to 5×10-6mol/L, the limit detection(S/N=3) of lead is 1.64×10-9 mol/L. And the repeated experiment and the recovery experiment showed that N-Cs/GCE sensor for detecting cadmium ions has a good stability of repeat is accuracy.Using this kind of sensor in detection of heavy metal Pb2+ and Cd2+ at the same time, and the mutual interference of Pb2+ and Cd2+ also were discussed. The results show that both of Pb2+ and Cd2+ has a good linear relationship between 1×10-7mol/L to 5×10-6mol/L, the limit detection(S/N=3) of Pb2+ is 1.12×10-9 mol/L., on the other hand, the limit detection(S/N=3) of Cd2+is 3.34×10-9 mol/L. According to the results of mutual interference experiment, we can find that the strength of the mutual interference between two kinds of metal ions are different; the mutual interference of Pb2+to Cd2+ is obvious.