Application Of Chemically Modified Electrode On The Analysis Of Environmental Pollutants

In this article,quaternary ammonium chitosan modified electrode,multi-wall carbon nanotubes modified electrode and the nano-alumina modified electrode were prepared on the glassy carbon electrode for the electrode substrate.Electrochemical behavior of nitrobenzene at three kinds of modified electrode and related experimental conditions was studied separately.The synthesis conditions of chitosan derivatives grafted multi-walled carbon nanotube was discussed preliminarily,the synthetic products were characterized and the electrochemical properties of the synthetic products were researched.1.Electrochemical behaviour of nitrobenzene based on nano-γ-Al₂O₃ modified glassy carbon electrode(NA/GCE) was studied.Some experimental parameters,such as amount of modifier,electrolyte solution and pH of electrolyte solution were optimized.The electrochemical reduction mechanism of nitrobenzene was discussed.The results showed that the modified electrode exhibited remarkable electrocatalysis on nitrobenzene in 0.2 mol·L^-1 potassium chloride solution.Nitrobenzene gives a quasi-reversible redox peaks at the NA/GCE over the potential range from -0.6 to 0 V.The reduction peak potential of nitrobenzene shifted negatively potential as pH values increased.2.Electrochemical behaviour of nitrobenzene based at multi-walled carbon nanotubes modified glassy carbon electrode(MWCNT/GCE) was studied.The electrochemical reduction mechanism of nitrobenzene was discussed.Some experimental parameters, such as amount of modifier,electrolyte solution and pH of electrolyte solution were optimized.The results showed that the modified electrode exhibited remarkable electrocatalysis on nitrobenzene in 0.2 mol·L^-1 sulfate solution.The reduction peak potential of nitrobenzene shifted positively from -440mV at bare GCE to -350mV at MWCNT/GCE,and the oxidation peak potential of nitrobenzene shifted negatively from 350mV to 300mV.The reduction peak current was found to be linearly related to concentration of nitrobenzene over the range 5.0×10^-7-4.2×10^-5 mol·L^-1,with a detection limit of 8.2×10^-8 mol·L^-1.This modified electrode has been used to determine the nitrobenzene in lake water samples.The recovery rate determined by means of standard addition method was between 98.3-100.6% 3.A new modified electrode was prepared based on the glass carbon electrode,which was coated with a film of 2-hydroxypropyltrimethyl ammonium chloride chitosan(HACC) through covalent-bond reaction.The electrochemical performance of the modified electrode(HACC/GCE) was studied by cyclic voltammetry(CV) and differential pulse voltammetry(DPV) methods.The results indicated that HACC/GCE had obviously electrocatalytic activity on nitrobenzene.The HACC/GCE showed good stability and repeatability in the test.There was an excellent linearity between reduction peak current and concentration of nitrobenzene in the range of 3.0 mg·L^-1-120 mg·L^-1(r=0.99941) in a Britton-Robinson butter solution(pH 1.0) with the detection limit of 0.7 mg·L^-1.4.A novel positively charged composite composed of 2-Hydroxy-propyltrimethyl ammonium chloride chitosan(HACC) and multiwalled carbon nanotubes(MWCNT) was synthesized by means of covalent reaction.The interaction between MWCNT and HACC was investigated and explained according to Fourier transform infrared spectroscopy(FTIR),thermogravimetric analysis(TGA) and transmission electron microscopy(TEM) results.The porous microstructure of the HACC-MWCNT modified electrode was observed by scanning electron microscopy(SEM).Its electrochemical properties were studied through zeta potential and cyclic voltammogram.The HACC-MWCNT maintained positively charged at any pH value investigated.The active area of MWCNT was increased greatly after grafted HACC.The HACC-MWCNT modifier also leads to a dramatic improvement in the electrostatic interactions between electrode and anionic complexes.These advantages of HACC-MWCNT/GC electrodes are illustrated from comparison to MWCNT/GC electrode.