Preparation Of Pesticide Residues Rapid Detection Card Based On Electrospinning And Its Properties

Organophosphorus（OPs）and carbamates（CMs）pesticides are two most commonly used pesticides currently,which could affect the human health even at a very low concentration.Therefore,it is of great significance to develop the rapid and reliable detection methods for determining these two pesticide residues in food.Rapid detection card has been widely used for pesticide residues detection due to its simplicity,convenience and low-cost,etc.However,various fixing materials including glass fiber and filter paper have been investigated for the preparation of the rapid detection card currently,and the sensitivity of these rapid detection cards still needs to be further improved.Recently,nanomaterials have also emerged as ideal carrier materials due to their high specific surface area and porosity.As a simple and mild technology,electrospinning can prepare nanofibers with small diameter and large specific surface area continuously,which has been widely applied in tissue engineering,filtration,medicine and other fields.However,its application in the fabrication of pesticide residuals rapid detection card has not been reported yet.Based on the characteristic of nanofibers,we speculate that the detection card based electrospun nanofiber may be superior in sensitivity.Therefore,we firstly discussed the feasibility of using electrospinning technology in preparing the rapid detection card for organophosphorus and carbamate pesticide residues detection.We compared the performance of fixed carriers prepared by adsorption method and encapsulation method and then determined the appropriate preparation method of the fixed carrier.On this basis,the obtained fixed carrier was characterized,and the performance of the prepared rapid detection card and its application in practical sample detection were studied.The main research contents and results of this paper are as follows:Firstly,the fixed carrier of pesticide residues card was prepared which was based on adsorption method by electrospinning,including polycaprolactone（PCL）fiber mat for substrate adsorption and PCL modified fiber mat for enzyme adsorption.By optimizing the spinning condition and modification conditions,the results were as following:PCL concentration was 125 g/L,the solvent composition was chloroform to methanol of 7:3,the electrospinning voltage was 13 k V,the electrospinning rate was 2.5 m L/h,and the electrospinning distance was 13 cm.The obtained PCL fiber mat had an average diameter of0.93μm with good morphology.The optimized modification conditions for the above obtained PCL nanofiber mat for was Na OH solution treatment for 1 h after being pro-infiltrated by 70%ethanol.The optimal adsorption time of enzyme and substrate were24 h and 12 h,respectively.Futhermore,the fixed carrier of pesticide residues card was prepared by electrospinning,including the enzyme fiber mat（EFM）prepared from the electrospinning solution of polyvinyl alcohol（PVA）and acetylcholinesterase（ACh E）mixture,and the substrate fiber mat（SFM）was prepared from the electrospinning solution of PVA and indole acetate（IA）mixture.For the EFM,the optimal PVA concentration was 75 g/L,and the optimal buffer of enzyme was KH₂PO₄-K₂HPO₄.The optimized spinning process parameters were 15 k V of the spinning voltage,0.3 m L/h of the injection rate,and 15 cm of the receiving distance.The obtained had uniform diameter（the average diameter of the fiber of 240 nm）with good morphology.For the SFM,optimal composition of substrate spinning solution were PVA concentration of 75 g/L and solvent of 15%ethanol,the optimized electrospinning process parameters were 12 k V of the electrospinning voltage,0.5 m L/h of the electrospinning rate,and 17 cm of the electrospinning distance.At last,the amount of fixed enzyme and the color developing time of the rapid detection card prepared based on the adsorption and the encapsulation process were compared.The results showed that the EFM prepared by the encapsulation method could fix more than 90%of the enzyme in the enzyme solution,and the color development time of the sample was the shortest.Therefore,the pesticide residues rapid detection card based was prepared based on the encapsulated method.After optimizing,the minimum effective concentrations of ACh E in EFM and IA in SFM were 1 mg/m L and 3 mg/m L,respectively.The characteristics of the fiber mat was characterized by ATR-FTIR,XPS,TG and DSC.The ATR-FTIR results showed that ACh E and IA were successfully encapsulated in the fiber mat.The thermal stability of EFM were significantly improved and the thermal stability of SFM were improved in a certain degree.Moreover,the kinetic study showed that the Km value of the enzyme in EFM was 9.16 m M,and the Km value of free enzyme was 5.58 m M.The optimal inhibition time and color development time of pesticide residues rapid detection card are 10 min and 5 min,respectively.Under optimized conditions,the detection limits of trichlorfon,omethoate,malathion,carbaryl and carbofuran were 0.2 mg/L,0.5 mg/L,0.1 mg/L,0.02 mg/L,respectively.All of results attained the detection limit of the national standard and are higher than the national standard.The rapid detection card has good storage stability,and can still be used normally after storaging at room temperature for 4 months.The self-made and commercial card were applied to detect the pesticide residues in actual samples of cabbage and apple.The results showed that the pesticide residues detection card based on electrospinning has higher sensitivity.This study provided the theoretical basis and experimental data for the development of a new type of pesticide residues rapid detection card,and will promote the application of electrospinning technology in the field of rapid detection.