The Preparation Of MWCNTs And IL Modified SPCE And Its Application Study In Analysis Of Lead And Cadmium

A novel modified electrode (MWCNTs-IL-SPCE) was prepared with multi-walled carbon nanotubes (MWCNTs) and l-butyl-3-methylimidazo-liu hexafluorophosphate ([BMIM]PF6) to modify screen-printed carbon electrode. Scanning electron microscope (SEM), cyclicvoltametry (CV), electrochemical impedance spectra (EIS) were used to characterize it. The stripping voltammetric responses of lead and cadmium were studied at this modified electrode, and then it was used to determine the content of lead and cadmium in food samples by stripping voltammetry.The main points of this thesis were as follow:1.The preparation and characterization of MWCNTs-IL-SPCE.0.02g MWCNTs and300μL [BMIM]PF6were pestled into paste, then coated a MWCNTs-IL film at electrode surface. The result of SEM showed that the paste could be coated equably. The CV and EIS results of modified electrode in K3[Fe(CN)6] solution indicated that the MWCNTs-IL film could speed up the electronic transfer rate at electrode surface. The investigation of lead and cadmium ions'stripping voltammetric responses at MWCNTs-IL-SPCE in buffer solution discovered that the stripping peak currents of lead and cadmium could be significantly enhanced and the stripping curves became steady by low concentration of iodine ion.2.The differential pulse stripping voltammetry using MWCNTs-IL-SPCE to detect lead was built. The optimum determination conditions of DPSV were:0.1mol/L NaAC-HAC buffer solution, pH value4.5,0.006mol/L I, deposition potential-1.1V, deposition time240s. Under this optimized conditions, the linearity, the equation and the detection limit were2-600μg/L,Y(μA)=0.23004+0.01965X(μg/L)(R=0.99926) and0.63μg/L, respectively. This method combined with double standard addition method and ICP-MS method were used to detect the trace lead in tea samples, no significant difference existed between two detection results after using t test.3.The square wave stripping voltammetry using MWCNTs-IL-SPCE to detect cadmium was built. The optimum determination conditions of SWSV were:0.1mol/L NaAC-HAC buffer solution, pH value4.5,0.004mol/L I, deposition potential-1.0V, deposition time300s. Under this optimized conditions, the linearity, the equation and the detection limit were10-500μg/L,Y(μA)=-0.45448+0.08275X(μg/L)(R=0.99886) and1.17μg/L, respectively. This method combined with double standard addition method and ICP-MS method were used to detect the trace cadmium in dried edible fungus samples, no significant difference existed between two detection results after using/test.4.The linear sweep stripping voltammetry using MWCNTs-IL-SPCE simultaneously to detect lead and cadmium was pilot studied. The sensitivity of LSSV is not good, but stripping peaks of lead and cadmium can well separate because of the high resolution. The optimum determination conditions of LSSV were:0.2mol/L NaAC-HAC buffer solution, pH value4.6,0.02mol/L I, deposition potential-1.1V, deposition time300s.The high sensitivity and good repeatability of these two methods demonstrated the application for a simple and economical determination of trace lead and cadmium in food samples.