Colorimetric Determination Of Organophosphorus Pesticides Based On Aptamer Gold Nanoparticle Probe

Organophosphorus pesticides have a very significant effect on crop income and pest control,so it has been widely used in agriculture and forestry.In recent years,the use of organophosphorus pesticides continues to increase.The excessive use of pesticides has caused pollution of crops,atmosphere,water and soil,and the residues of organophosphorus pesticides in food or crops may spread through biological amplification of the food chain,causing harm to the health of organisms at the end of the food chain.Therefore,the development of rapid and simple detection methods for organophosphorus pesticide residues has important and far-reaching significance for human health and safety,ecological environmental protection and food safety.The variation of particle size,morphology and distance between particles will affect the optical properties and macroscopic phenomena of Au NPs,which is manifested by the change of color of the gold nanoparticles.Aptamers are easy to synthesize,have good biological stability and strong specificity,and are widely used in the field of analysis and testing.Based on the unique optical properties of nano-gold,this paper proposes a rapid colorimetric method for detecting organophosphorus pesticides.The specific research content is as follows:1)Based on the fact that the gold nanoparticles can be agglomerated and the color of the solution changes from red to blue,a rapid and simple method for the determination of the gold nanoparticles without any modifier was established.By investigating different particle sizes of gold nanoparticles,different p H values and concentrations of acetoacetate-sodium acetate buffer solution,and the interaction time between methyl valley thiophosphate and gold nanoparticles,the absorbance ratio is the highest when the particle size of gold nanoparticles is 13 nm,the buffer solution pH=5.0,C=0.03 mol/L and the interaction time is 50 min.Under optimized experimental conditions,the determination of lake water samples was completed.It is concluded that,under acidic conditions,the protonation of N and S in the bond of thiophos in the molecule of methyl glutamate is formed to form-NH and-SH,and S-Au is formed to form-SH and Au,so that the molecule of methyl glutamate is connected to the surface of gold nanoparticles,and the hydrogen bond of-NH and O in another molecule is formed to shorten the distance between the gold nanoparticles and aggregate,and the color of the solution is changed accordingly.There was a good linear relationship between 0.21-0.47 μmol/L and 0.05-0.16μmol/L.The visual detection limit was 0.10 μmol/L,and the UV-VIS detection limit was5.86 nmol/L.The results of recovery experiment and determination of lake water sample are satisfactory.2)Based on the principle of nano-gold colorimetric comparison between the aptamer and the aptamer,the concentration of the cationic polymer PDDA and the aptamer were investigated,and the maximum absorbance ratio difference was determined when the concentration of PDDA was 12 nmol/L and that of the aptamer was 4 nmol/L.The determination of lake water samples was completed under optimized experimental conditions.When there is no thiophosphate in the detection system,PDDA combines with aptamer to form a structure similar to "DNA double strand".At this time,the negatively charged gold nanoparticles are uniformly dispersed in aqueous solution.When there is thiophosphorous water in the detection system,thiophosphorous water selectively combines with thiophosphorous water aptamer to form a relatively stable complex.Therefore,positively charged PDDA cannot combine with the aptamer,but agglutinates with nano-gold,and the solution color changes from wine red to blue purple.Methods The detection limit of UV-VIS was 5.76 nmol/L,and the linear detection range was 0-480nmol/L.At the same time,some organic thiophosphate compounds did not interfere with the detection system.The results were satisfactory.In this paper,a colorimetric-ultraviolet method based on agglomeration principle is proposed for the determination of organothiophosphorous compounds such as methyl glutaphosphorous.The detection time of this method is short,which can meet the needs of field detection.A cationic polymer(PDDA)based on aptamer was developed for the determination of thiophosphorus hydroamides.The detection limit of UV-VIS is lower than the national standard,the detection time is short,and the method has good specificity and anti-interference,which is expected to be used in field detection.