Simultaneous Determination Of O-,m-,p- Chlorophenol By MWNT Modified Glassy Carbon Electrode With The Aid Of Artifical Neural Network

This paper firstly studied the electrochemical behavior of chlorophenol at the glassy carbon electrode modified with multi-wall carbon nanotube(MWNT).It is found that the oxidation peaks of the three isomers of chlorophenol were strongly overlap to detect them separately. Therefore, a new method of the combination of MWNT modified glassy carbon electrode with artifical neural network was developed to establish a model to detect the three isomers of chlorophenol separately.The proposed method may solve the problem the separate detection of the three isomers of chlorophenol.Then the glassy carbon electrode was modified with multi-walled carbon nanotubes (MWNT), chitosan (CHI) and ionic liquid to constructed the modified electrode,MWNT-CHI-IL/GCE.The electrochemical behaviors of MWNT-CHI-IL/ GCE was studied with cyclic voltammograms, and the MWNT-CHI-IL/GCE was used for the determination of trace amounts of the three isomers of chlorophenol.In addition, the effect of ionic liquid,[BDmim]PF6,on the electrochemical behaviors of the modified electrod was studied with Linear sweep voltammetry,chronocoulometry and alternative current impedance spectroscopy.The main conclusions of the dissertation were as follow:1.The electrochemical characteristics of the three isomers of chlorophenol at MWCNT modified electrod. In 0.1mol/L PBS (pH=7.0), a sensitive irreversible oxidation peak of each the three isomers of chlorophenol on the modified electeode was detected .The peak potentials were 624mV,712mV and 632mV for 2-,3-,4-chlorophenol, respectively.Under the optimal conditions,the peak currents were linear with the concentration in the rang of 2.07～103.66μmol/L for 2-chlorophenol,1.62～138.60μmol/L for 3-chlorophenol and 2.71～108.48μmol/L for 4-chlorophenol, respectively.The detection limits were 0.9μmol/L for 2-chlorophenol, 0.1μmol/Lfor 3-chlorophenol and 0.8μmol/Lfor 4-chlorophenol,respectively.However,the oxidation peaks of 2-chlorophenol and, 4-chlorophenol overlapped severely.2.The construction of the model for the simultaneous determination of the three isomers of chlorophenol with MWNT modified glassy carbon electrode-artifical neural network. Based on the analytical results of the cyclic voltammograms of the mixture of 2-,3-, 4-chlorophenol ,with Radial basis function-artificial neural network (RBF-ANN), the model for the simultaneous prediction of the three isomers of chlorophenol was established.The relative prediction errors of each isomer were 9.51%,6.11% and 8.86%.The total relative prediction error (RPET) was 7.87%.Experimental results revealed that both the relative prediction errors of each isomer and the total relative prediction error were better than the result suggested that the RPF-ANN approach was better than that of the partial least square(PLS) method.Therefore,RBF-ANN could be a suitable mathematical method to solve the problems of nonlinearity, multivariable calibration and resolution of the three isomers of chlorophenol.The suggested method could be used for the simultaneous determination of the three isomers of chlorophenol and was applied for the determination of 2-,3-,4-chlorophenol in synthetic samples with the recoveries between 96.93% and 101.75%.3.The electrochemical characteristics of MWNT-CHI-IL/GCE.The electrochemical behaviors of the modified electrode were studied with CV in the solution of 2mmol/L K3[Fe(CN)6].Experimental results illustrated that MWNT-CHI-IL/GCE showed higher sensitive and better reversible than that of GCE.The stability and the reversibility of the modified electrode were also improved with proper amounts of the modified solution(2μL).4.Determination of of the three isomers of chlorophenol with MWNT-CHI-IL/GCE. Under the optimum determination conditions of differential pulse stripping voltammogram (DPSV) when MWNT-CHI-IL/GCE was used as working elelctrode,the oxidation currents of 4-chlorophenol,3-chlorophenol and 2-chlorophenol were linear with the concentrations of 8.0×10-7～1.5×10-4mol/L,6.0×10-7～1.1×10-4mol/Land9.0×10-7～2.0×10-4mol/L.The detection limits of the three isomers were 8.0×10-8mol/L,4×10-8mol/L and1.0×10-7mol/L, respectively.The influences of the co-existing substances in water samples were studied.It was found that those co-existing substances did not interfere the detection of the three isomers of chlorophenol except for phenol and resorcinol.Moreover, the interference among the three isomers of chlorophenol was investigated.Experimental results revealed that one isomer of chlorophenol could influence another.Therefore,MWNT-CHI-IL/GCE was hard to determine the three isomers of chlorophenol simutanously.5.The effect mechanism of ionic liquid on MWNT-CHI-IL/GCE.Linear sweep voltamme- try,chronoamperometry and alternative current impedance spectroscopy were adopted to study the effect of ionic liquid on the adsorption performance of 4-chlorophenol and the electron transfer rate of MWNT-CHI-IL/GCE.Experimental results showed that the addition of [BDmim]PF6 could modify the surface characteristics of modified electrode, induce the adsorption capacity of 4-chlorophenol on the surface of the modified electrode from 45.8μc to 84.38μc.It also could found that the addition of ionic liquids could enhance the conductivity capacity of the membrane and accelerate the rates of electronic transfer,which indicated that the procese of electrode reaction controlled by electron transfer was weaken and the procese of electrode reaction controlled by diffusion was raised.