Development Of Colorimetric Enzyme Tablets For Rapid Pesticide Residues Detection Based On The Catalytic Activity Of Nanomaterials Mimetic Enzyme

Organophosphorus pesticides?OPs?are widely used to control crop diseases and insect pests due to the high efficiency and broad spectrum.However,OPs have certain of toxicity,and will threaten human health and ecological environment if improperly used or excessive residue.Therefore,the detection of organophosphorus pesticides is of great significance.Traditional detection methods are mainly including chromatography,immunoassay,and fluorescence method and so on,but these methods are complicated and not conducive to field detection.Enzyme inhibition techniques has the advantages of simple operation and high accuracy,herein some rapid detection products of organophosphorus pesticides like kit,colorimetric enzyme tablets and test strip based on this method have been developed.In recent years,it has been found that many nano materials have mimic activities such as peroxidase and oxidase,and so on,which can catalyze the oxidation of substrates and produce color changes under certain conditions.There are few literature utilize nanoenzyme to construct sensors for rapid detection of organophosphorus pesticides at present.Therefore,the colorimetric enzyme tablets for rapid rapid detection of dimethoate and glyphosate based on the inhibition effect of organophosphorus pesticides on the catalytic activity of AuNPs and porous Co₃O₄ were developed in this paper.The main contents of this article are as follows:?1?A colorimetric enzyme tablets based on inhibiting the catalytic activity of AuNPs was developed.Our previous research found that dimethoate can effectively inhibit the catalytic activity of AuNPs.Herein,we plan to transfer the sensing system to solid-phase materials,and prepared the AuNPs enzyme tablet after analyzing the feasibility of solid-state reaction.Firstly,the carrier membrane for immobilize AuNPs and the formula of blocking liquid to pretreat carrier membrane were explored.Secondly,we investigated the effects of salt ion concentration,AuNPs concentration,substrate concentration,pre-reaction time and reaction temperature on the detection results in order to improve the detection performance of colorimetric enzyme tablets.Under the optimal detection conditions,the detection limit of colorimetric enzyme tablets for dimethoate was 800?g/L,and also had good specificity.The average recoveries of dimethoate were in the range of 88.5%-95.6%in actual samples,which indicated that the colorimetric enzyme tablets had good accuracy and stability in prctical application.?2?We developed a colorimetric enzyme tablets for the detection of glyphosate based on the inhibition of porous Co₃O₄ catalytic activity.First of all,the inhibition process of glyphosate on the catalytic activity of porous Co₃O₄ was explored,and we found that in the absence of glyphosate,the H₂O₂ could decomposed hydroxyl radicals?·OH?and impelled the oxidation of TMB to form Blue products.However,in the absence of glyphosate,the catalytic activity of porous Co₃O₄ was inhibited and the oxidation ability to TMB was weakened,so that the sensing solution was colorless.In order to transfer the detection system to solid-phase materials,we analysis the feasibility of solid reaction,and prepared the enzyme tablets of porous Co₃O₄.In the process of preparing enzyme tablets,the carrier membrane and the formula of sealing solution to pretreat the carrier membrane,which has a great influence on the immobilization of porous Co₃O₄ were studied.Then,to obtain higher sensitivity of the colorimetric enzyme tablets,we explored the effects of some key parameters,such as salt ion concentration,porous Co₃O₄ concentration,substrate concentration,pre-reaction time,detection time and reaction temperature on the detection of glyphosate were explored.In the optimum conditions,the detection limit of glyphosate was 700?g/L,and other competitive pesticides will not interfere with the detection process.The recoveries rates of glyphosate in the actual sample detection were 89.0%-96.1%,indicating that the colorimetric enzyme tablets have great accuracy and stability.In conclusion,colorimetric enzyme tablets for the detection of dimethoate and glyphosate based on the simulated enzyme catalytic activity of AuNPs and porous Co₃O₄,were developed in this paper.They have the advantages of short detection time,high sensitivity,simple sample pretreatment and visual identification,so they are expected to be applied in the detection of organophosphorus pesticide residues in agricultural products.