Research On Analysis And Detection Of Trace Pesticides With Novel Multifunctional Enrichment Materials

Pesticides are important parts of modern agricultural production,and the use of pesticides has made outstanding contributions to improving crop yield and quality.However,with the non-standard use of pesticides,the problem of pesticide residues has also attracted human attentions.Although the residual concentration of most organic pesticides is low,they usually have the characteristics of high toxicity,long half-life,slow natural degradation and biological accumulation,which are potentially risk for human health and food safety,and may also cause great harm to the environment.Therefore,to ensure food safety and human health,a simple,efficient and sensitive method to detect pesticide residues in real environmental samples and food samples is urgently needed.In this paper,two adsorbent materials were synthesized to remove pesticide residues in environmental water samples and food samples,and were detected in the combination of HPLC-UV and colorimetric detection methods.The following contents are as follows:1.The ionic liquid(IL_COOH)with carboxyl functional groups was confined in carbon nanotube（CNT）by post-confinement strategy to obtain IL_COOH@CNT,and combined with the magnetic solid phase extraction（MSPE）and the method of HPLC-UV to analyze the residual amount of five PUHs in cucumber,river water and tea water samples.The experimental parameters of the MSPE process were optimized by univariate and the adsorption kinetics and adsorption capacity were explored under the best experimental conditions.It is found that the dynamic adsorption conforms to the pseudo-second-order kinetic model,and the adsorption capacity of the five PUHs can reach 7.209,4.943,7.702,11.665 and 12.829 mg g^-1,respectively.IL_COOH@CNT has a higher adsorption capacity than the original CNT.The adsorption mechanism of IL_COOH@CNT on PUHs can be attributed to hydrogen bonding interactions,π-πinteractions,hydrophobic interactions,electrostatic interactions,and pore size selection.Under the best experimental conditions,the method has a good recovery（85.0%-108.7%）,a lower detection limit(0.11-0.14 ng m L^-1),and a higher EF（131-185）.Finally,a laboratory-syringe-device was developed for the extraction of PUHs in actual samples.The device has a high recovery rate in practical applications and has good application prospects for rapid,convenient and effective detection.2.Ni-NCP,a multifunctional carbon material doped with Ni and N,was prepared for the adsorption and colorimetric detection of carbamate pesticides in food samples.The experimental conditions of dispersed solid phase extraction（d SPE）were optimized.The adsorption capacity and adsorption mechanism were studied.The adsorption capacity of Ni-NCP was 11.71,51.67 and 5.70 mg g^-1,respectively.The main adsorption mechanisms were hydrogen bond interactions,π-πinteractions,electrostatic interactions and van der Waals forces.In addition,the oxidase-like activity and peroxidase-like activity of Ni-NCP were explored through a series of experiments,and the best catalytic performance of Ni-NCP was guaranteed by optimizing the p H of sample solution,reaction temperature,reaction time and the concentration of Ni-NCP.Using free radical capture experiment and XPS analyzed the reason of Ni-NCP has good enzyme-like activity:due to the presence of the Ni-N site,Ni-NCP has high electron transfer rate,which can oxidize dissolved oxygen and H₂O₂to O₂·^-,¹O₂and·OH respectively.These radicals are highly oxidative and can strip electrons from the TMB to produce ox TMB,which can change the color of solution.Using the inhibitory effect of Carbayl on ACh E activity and the reducing effect of choline on ox TMB,we established a method with simple operation,good selectivity and high sensitivity.This method has good linearity in the concentration range of 0-30 ng m L^-1,with a quantitation limit of 5 ng m L^-1,and has good selectivity and anti-interference ability.Moreover,the detection results of this method in real sample detection were similar to those of the d SPE-HPLC-UV method,revealing this method has a good practical feasibility.Finally,a colorimetric detection strategy based on smartphone and Ni-NCP hydrogel balls was successfully developed for the portable detection of pesticides.The linear range of this strategy is 5-100 ng m L^-1,the detection limit is 1.5 ng m L^-1,the recovery rate is 95.6-98.5%,and this strategy has the advantages of good analysis performance,fast analysis speed,simple operation and portability,which shows great application potential in the field of Carbyal detection.