Study On Preparation And Application Of Four Amide Pesticide Molecularly Imprinted Electrochemical Sensors

In recent years,the detection rate of amide fungicides in melons,fruits,vegetables and tobacco from some areas of China is relatively high,but if these fungicides enter the environment or human body in large quantities,they will affect the environment and human body,so it is necessary to detect them.However,the current detection methods of amide fungicides have some shortcomings,such as expensive equipment,high detection cost,long detection cycle,and need professional operation.The molecularly imprinted electrochemical sensors have the advantages of high sensitivity,low detection limit,simple operation,low preparation cost and wide application.This paper have prepared and studied four different amide fungicides molecularly imprinted electrochemical sensors(metalaxyl,flumorph,benalaxyl and dimethomorph),the specific contents are as follows:1.Metalaxyl molecular imprinting electrochemical sensor based on polypyrogallol modification.According to the enrichment effect of hydroxyl groups in polypyrogallol(PPG)on metalaxyl(MA),and using polypyrogallol film as signal amplifying element,a polypyrogallol modified glassy carbon electrode(PPG/GCE)was prepared by electropolymerization on the surface of glassy carbon electrode.Combining the advantages of electrochemistry and the principle of molecular imprinting technology,the imprinting film was prepared on the surface of PPG/GCE using metalaxyl as template and phenol as functional monomer.Under the optimized conditions,the response current of the sensor to metalaxyl ?I(?A)showed a good linear relationship with the concentration of metalaxyl in the range of 3.00×10-10?4.24×10-6 mol/L.The linear regression equation is?i=6.524+3.987c(?mol/L)(r=0.9999).The detection limit(S/N=3)was 1.01 × 10-10 mol/L.The sensor was applied to the determination of metalaxyl in cucumber and tomato samples,the recovery was between 99.6%and 107.5%,and the relative standard deviation was less than 4.5%.Moreover,the selectivity,reproducibility and stability of the sensor are ideal.Ten times of dimethomorph,fluomorph,benalaxyl and 50 times of dimethoate and chlorothalonil have no effect on the detection of metalaxyl.2.Flumorph molecularly imprinted electrochemical sensor based on nickel oxide doped graphene modification.A novel Flumorph Molecularly Imprinted Electrochemical Sensor(FM-MIM/NiO-GR/GCE)based on nickel oxide doped graphene was constructed by in situ polymerization of flumorph(FM)as template molecule,acrylamide and o-phenylenediamine as functional monomers on the surface of nickel oxide doped graphene modified glassy carbon electrode(NiO-GR/GCE).Under the optimized conditions,the sensor has good response selectivity and high sensitivity to flumorph.The concentration c of flumorph in the range of 3.00 × 10-9?-8.42×10-8 mol/L and 8.42×10-8?4.89×10-5 mol/L has a good linear relationship with the change of peak current.The linear regression equations are ?i=8.51+189.50c(r=0.9999)and ?i=25.47+0.13c(r=0.9999),respectively.The detection limit(S/N=3)is 1.25 ×10-10 mol/L.Although there are 50 times of dimethomorph and benalaxyl,10 times of metalaxyl,chlorothalonil and dimethoate in the solution at the same time,it does not interfere with the determination of flumorph by the sensor.The RSD value was less than 3.0%and the recovery was between 99.0%and 102.0%.3.Benalaxyl-imprinted screen-printed electrode modified by redox graphene.Firstly,redox graphene was used as an electrochemical signal amplifier element to prepare redox graphene modified screen printed electrode(RGO/SPE).Then a redox graphene-based molecularly imprinted polymer film was synthesized on RGO/SPE,using benalaxyl(BA)as template molecule and acrylamide as functional monomer,and initiated by ultraviolet light.Finally,the Benalaxyl Molecularly Imprinted Electrochemical Sensor(BA-MIM/RGO/SPE)modified by redox graphene was constructed.The response current Ai and the concentration c of BA were linearity between 7.0 ×10-9?2.4 × 10-7 mol/L and 2.4 × 10-7-6.8×104 mol/L under the optimized conditions.Their linear regression equations were ?i =0.4737+26.8745c(?mol/L)(r=0.9999)and ?i=6.9203+0.0018c(?mol/L)(r=0.9997).The detection limit(S/N=3)was 1.0 × 10-9 mol/L.Besides,the detection of benalaxyl was not interfered by 30 times of dimethomorph,flumorph and metalaxyl,and 80 times of dimethoate and chlorothalonil.The RSD of benalaxyl in tobacco samples was less than 3.5%,and the recovery of it was between 101.0%and 107.2%.4.Molecularly imprinted carbon paste electrode based on vinyl carbon nanotubes was studied.A Dimethomorph Imprinted Carbon Paste Electrode(DIM-MICPE)was fabricated by surface imprinting technique using dimethomorph(DIM)as template molecule,vinyl carbon nanotubes(CNTs)as carrier,a mixture of 4-vinylpyridine and a-methacrylic acid as functional monomer,and A Dimethomorph Imprinted Carbon Paste Electrode(DIM-MICPE)was constructed by doping polymer with graphite powder.The response current ?i(?A)of the electrode has a good linear relationship with the dimethomorph concentration in the range of 3.5×10-9?2.2 × 10"6 mol/L and 2.2 × 10-6?1.2 × 10-4 mol/L.The linear regression equations are Ai=5.84+11.03c(?mol/L)(r=0.9995)and ?i=29.98+0.24c(?mol/L)(r=0.9991).The detection limit(S/N=3)was 9.0 × 10-11 mol/L.The method was applied to the determination of dimethomorph in tomato and grape samples.The RSD values were within 4.0%,and the recovery was 98.0-103.0%.