Study On Rapid Detection Of Soil Pesticide Residues Based On Surface Enhanced Raman Spectroscopy

With the development of human agriculture and economy,pesticides play a very important role in increasing crop yields.However,in recent years,the long-term application or even abuse of pesticides,especially the use of highly toxic,high-residue and refractory pesticides,has caused the problem of farmland soil pollution as well as the destruction of the ecological environment,threatening the human health and environmental sustainability.Therefore,the rapid access of pesticides residues information in soil is conducive to repairing the soil,protecting the environment,and ensuring food safety.Although traditional methods for detecting soil pesticides have the advantages of being high sensitivity and good repeatability,those methods are limited with the expensive reagent and time-comsuming process.Surface enhanced Raman scattering(SERS),as a kind of spectral detection technology,shows the advantages of fast detection speed,non-destructive detection,high sensitivity,strong anti-interference ability,and portable instrument,which can realize the rapid detection of soil pesticide residues.This study takeed soil as the object,mainly solved the problems of the detection of three pesticide residues in soil,including chlorpyrifos,deltamethrin and carbofuran,and improved the SERS accuracy and the limit of detection(LOD).This paper mainly included three aspects,firstly,the effect of heating reaction time and the amount of trisodium citrate on the structure and particle morphology of gold nanoparticles(AuNPs)was explored.Secoendly,the optimal experimental conditions for the detection of three pesticides by SERS were explored.Thirdly,the qualitative identification and quantitative model for the detection of three pesticides in soil were established,which provides theoretical basis and technical support for the research of pesticide residue detection and control in soil.The main conclusions are as follows:(1)The size and morphology of AuNPs were affected by the amount of trisodium citrate and the heating reaction time,and there was a good linear relationship between the size of AuNPs and SERS signal intensity.The results showed that:(1)When trisodium citrate increased from 0.5 mL to 4 mL,the diameter of AuNPs decreased from 41 nm to 13 nm,and there were good linear correlations between the signal intensity of chlorpyrifos,deltamethrin and carbofuran SERS and the diameter of AuNPs,with R2 of 0.997,0.9647 and 0.9606,respectively.(2)When the dosage was 0.5 mL and the heating reaction time increased from 10 min to 30 min,the diameter of AuNPs ranged from 40 to 50 nm.The heating time affected the agglomeration of AuNPs and SERS signal,and the AuNPs could be excessive agglomerated when the heating time was too long or too short.When the reaction time of 100 mL of 0.01%perchlorauric acid and 0.5 mL of trisodium citrate was 25 minutes,the AuNPs were the most stable and dispersible.(2)The AuNPs substract,the regulator,and the ratio of AuNPs and soil extract for the SERS signal enhancement of the three pesticides in soil were optimized.The experimental resulted were as follows.Firstly,when the AuNPs prepared by the reaction of 100 mL of 0.01%chloroauric acid and 1 mL of trisodium citrate and the heating reaction time was 25 min,the SERS signal intensities of chlorpyrifos,deltamethrin and carbofuran were the highest in soil.Secondly,the optimal regulator for chlorpyrifos SERS signal enhancement was NaBr,the optimal regulator for deltamethrin SERS signal enhancement was KI,and the optimal regulator for carbofuran SERS signal enhancement was KCI.Thirdly,when the ratio of AuNPs to soil extract was 6:1,the SERS signal intensity of chlorpyrifos and deltamethrin were the highest,and when the ratio of AuNPs to soil extract was 2:1,the characteristic peak SERS signal intensity was the highest.(3)The multivariate and univariate models of pesticide residues in soil based on the intensity and area of characteristic peaks were established,and the detection of three pesticide residues in soil based on SERS technology was realized.The experimental results were as follows.Firstly,when the original spectra were processed by multivariate scatter correction(MSC),and modeled by the partial least squares(PLS),the prediction effect was the best.The prediction effect order of the three pesticides in the soil was chlorpyrifos(Rp2 = 0.9740;LOD=0.025 mg/kg),deltamethrin(Rp2 = 0.9176;LOD = 0.056 mg/kg)and carbofuran(Rp2 = 0.8517;LOD = 0.053 mg/kg).Secondly,340,459,529,610,674 and 1270 cm-1 could be used as quantitative peaks of chlorpyrifos residues in soil.560 and 1000 cm-1 could be used as the quantitative peaks of deltamethrin residues in soil,and 1000,1299,1436 and 1614 cm-1 could be used as quantitative peaks of carbofuran residues in soil.In summary,this study prepared a suitable SERS substrate for the detection of three soil pesticides residues,proved the influence law between different materials,morphology and signal enhancement,as well as improved the LODs of three different pesticide residues,which provides a scientific theoretical basis for soil environmental restoration and sustainable development.