Electrochemical Detection Of Organophosphorus Pesticides Based On Amino Acids Conjugated Nanoparticles Modified Electrodes

Organophosphorus pesticides(OPs)are among the most widely employed pesticides world-wide due to their high half-life time,the incorrect use and residues of OPs result in serious contamination in agricultural products and the environment.Until now,the widely used methods for determination of OPs sometimes require relatively expensive materials or more organic solvents and need complex pre-processing.Thus,there is a demand for new analytical technique with cheap instrument,low cost,simple operation,time saving and real-time detection for OPs.In this work,amino acids(AAs)serine(S),histamine(H)and glutamic acid(E)attached nanoparticles were found to help catalyze hydrolysis of organophosphorus pesticides(OPs)to fonn electroactive p-nitrophenol(PNP).This phenomenon follow the mechanism of proton transfer relay found in biomimetic hydrolases.So an electrochemical method using S,H,E conjugated TiO2 nanoparticles(NPs)as modifier to detect organophosphorus pesticides was developed.TiO2 NPs were used as carriers,first coated with dopamine(DA)via the interaction between enediol groups and metal sites.And then the amine groups were bound with anino acids via EDC-NHS cross-linking agents to produce S,H,E sites triminated composite nanomaterials with high stability.The attached AAs also have hydrolyzing activity toward hydrolysis of OPs.The prepared TiO2 NPs-AAs composites were characterized by scannuing electron microscopy and elemental analysis showed the presence of AAs sites.The coverage or surface density of AAs was quantified by fluorescence spectrum analysis.AAs(S,H,E)were connected to the amination of TiO2 to form amide bonds between DA and AAs by the cross-linking of EDC-NHS.The coverage of AAs was about 1.81×1014 molecules/cm2 TiO2.No obvious detachment of AAs or DA was observed during the working period in neutral or acidic solutions(pH 7.0).OPs(methyl paraoxon,methyl parathion and ethyl paraoxon)can be catalytically hydrolyzed at the TiO2 NPs-AAs composites modified electrode surface and produce PNP.So OPs existed can be quantified via the electrochemical signals of PNP.The detection limit of OPs were about 500 nM.Finally,this detection technique was applied into the assay of OPs in real samples(Lactuca sativa L)and the detection accuracy was studied by comparison with the standard GC-MS method.