Application Of Electrospray-ion Mobility Spectrometry In Rapid Detection Of Pesticide Residues In Fruits And Vegetables

The problem of pesticide residues is a serious threat to public food safety.The traditional detection method,such as chromatography-mass spectrometry,has the disadvantages of expensive,complex test conditions,long analysis time,and inability to detect on-site.Ion mobility spectrometry（IMS）is a rapid gaseous ion detection technique widely used in the detection of drugs and explosives.Now it has aroused great interest for researchers in the field of pesticide residue detection.This low cost,fast analysis speed and high sensitivity method became available.The emergence of an electrospray ionization（ESI）source has broadened the application scope of IMS,which can analyze volatile and non-volatile pesticides.In addition,IMS can work at atmospheric pressure and has better portability than Mass spectrum（MS）,so it is suitable for on-site detection.Based on ESI-IMS,this paper established a series of rapid detection methods for pesticide residues in fruits and vegetables according to the current problems in pesticide residue detection.The details are as follows:1.Aiming at the problem of the urgent need for rapid on-site detection technology in the field of pesticide residues,a method for rapid non-destructive detection of five pesticide residues in fruit and vegetable peels was established based on ESI-IMS combined with a surface swab method.The experiment first optimized the ESI voltage deviation of 4.5 k V,the injection flow rate of 0.5μL/min,and the migration tube temperature of 120℃.Under the optimal instrumental conditions,the LOD of the detected pesticides was between 3.6-55.1μg/L.The experiment also determined that the swab material of the surface swab method was polyester fiber swab,the swab was pre-soaked with methanol-water（9:1,v/v）,and the eluent volume was 2 m L.Finally,this method was applied to pesticide detection in apple,pear,and tomato peels,and the results showed that the spiked recovery was between 71.4-121.2%.This method has the characteristics of rapid and non-destructive.It could be widely used in rapid on-site pesticide screening.2.Considering that ESI-IMS is susceptible to matrix interference,a rapid detection method of eight pesticide residues in apples by solid phase extraction（SPE）-ESI-IMS and low-temperature purification（LTP）-ESI-IMS was established.The optimized extraction solvent of SPE was methanol;the optimized freezing time of LTP was six hours,and the PSA amount was 500 mg.The results showed that the LOD of the pesticides after SPE and LTP pretreatment were between 0.02-0.09 mg/kg and 0.02-0.12 mg/kg,respectively,and the recoveries were between 62.0-114.8%and 67.9-115.4%,respectively.As general pretreatments,SPE and LTP combined with ESI-IMS can meet the requirement of Chinese standards.3.In order to solve the low resolving power of IMS and the long time of pre-separation methods,such as chromatography,a metal ion-assisted-ESI-IMS method was established for the rapid and simultaneous detection of carbendazim and thiabendazole residues in fruits.This method changed the drift time of thiabendazole through the metal addition of Cu²⁺and thiabendazole without using pre-separation methods,such as chromatography,and solves the overlapping of carbendazim and thiabendazole peaks on ESI-IMS.The method was used to detect carbendazim and thiabendazole in apples,pears,bananas,and mangoes.The LODs were 0.01-0.03 mg/kg and 0.04-0.13 mg/kg,respectively,the spiked recoveries were between 61.5-122.0%and 83.5-119.8%,and the RSD was less than 13.9%,indicating that this method can realize the quantitative analysis of multiple pesticide residues.In addition,based on density functional theory,the theoretical structure of metal complexes was calculated.The feasibility of simultaneous detection of carbendazim and thiabendazole by ESI-IMS was theoretically explained based on molecular electrostatic potential analysis and binding energy calculation.