Methodology Of Fast Detection Of Pesticide Residues By Multi-Frequency Amplitude Pulse Electronic Tongue

The application of pesticides has greatly promoted the development of modern agriculture.However,with the increase in the variety and dosage of pesticides,the problems caused by pesticide residues in food and environment have become more and more serious,and its harm to human health and environment has aroused wide international attention. So it is imperative to develop a simple and rapid detection method for pesticide residues.In this paper,a novel electronic tongue——multi-frequency amplitude pulse electronic tongue(MFP-ET) was used to detect two widely used pesticide:organophosphorous pesticide and pyrethroid pesticide.The sensor part of MFP-ET——a standard three-electrode system was consisted of several metallic working electrodes,a Ag/AgCl reference electrode and a pillar platinum electrode as counter electrode. The innovative aspect in this electronic tongue is the application of a new electrochemical method——the multifrequency large amplitude pulse voltammetry(MLAPV) which is very useful for discriminating samples in the voltammetric electronic tongue by applying three frequency segments,1 Hz,10 Hz and 100 Hz.Multivariate data analysis(MVDA) such as Principal component analysis(PCA),Partial Least Squares(PLS), Soft Independent Modeling of Class Analogy/Statistical Isolinear MultiCategory Analogy(SIMCA),Principal Component Regression (PCR) was often used to analyzing the data from the electronic tongue. With the advantages of rapid detection and simple sample preparation, MFP-ET seems to be suitable for detecting the pesticide residues.The main research work is as follows:(1) Qualitative discrimination of pesticides using MFP-ET.Seven pesticides(dichlorovos,phoxim,malathion,acephate, fenvalerate,cypermethrin,deltamethrin) were discriminated with MFP-ET through a sensor array of platinum,gold,palladium,cuprum, titanium and cadmium electrodes under the mentioned three frequency segments of 1 Hz,10 Hz and 100 Hz.Principal component analysis was used to process the data.The results showed that the pesticides could be successfully discriminated by combining together palladium electrode in 100 Hz,cadmium electrode in 10 Hz and cuprum electrode in 10 Hz.(2) Quantitative detection of three pyrethroid pesticides,fenvalerate, cypermethrin and deltamethrin using MFP-ET.On the basis of the methodology for application of MFP-ET,firstly, PCA was used to determine which sensor array for MFP-ET was the best one to distinguish three pyrethroid pesticides(fenvalerate,cypermethrin, and deltamethrin).The result showed that the suitable sensor array was compose of platinum electrode in 1 Hz,palladium electrode in 10 Hz and gold electrode in 1 Hz.Then,MFP-ET with this suitable sensor array was adopted to detect the concentrations of the three pesticides and the data were analyzed by SIMCA.The lowest detectable concentrations for fenvalerate,cypermethrin,and deltamethrin in absolute ethanol were 1.00 mg/L,0.80 mg/L and 0.70 mg/L respectively.Within the above detection ranges,the contents of three pyrethroid pesticides,fenvalerate,cypermethrin and deltamethrin in the composite solution were quantified.MFP-ET was used to quantify the calibration sample composed of these three pesticides.The model were established by experimental data processing with PLS and PCR.The established model was used to predict the concentrations of the components in the prediction sample.The final result demonstrated that PLS gave a better discrimination among the three components than PCR did with the relative prediction errors(RPE_T) being at 7.8%and 10.6%respectively.MFP-ET showed a promising application in qualitative and quantitative analysis of pesticides,based on selecting the appropriate sensor array composed of the different non-modified metal electrodes and combining together the different frequency segments of multifrequency large amplitude pulse voltammetry.