Research On Rapid Analysis And Degradation Of Organophosphorus Pesticides Using Ambient Plasma-based Mass Spectrometry Technology

Organophosphorus pesticides（OPPs）,as a kind of high-efficiency and broad-spectrum insecticides,are widely used in various agricultural production.However,this agricultural development aimed at increasing production may lead to the overuse of pesticides,causing in the long-term accumulation of these highly toxic chemicals in food and the environment,resulting in serious pesticide residues.Therefore,the rapid detection and degradation of OPPs is of great significance to food safety and environmental protection.Conventional approaches such as chromatography-mass spectrometry have the limitations of complicated procedures,time-consuming,and high cost.They are not suitable for the rapid analysis of OPPs,and the rapid inspection of OPPs still faces huge challenges.In recent years,ambient mass spectrometry technology has been used in the rapid detection of pesticides due to its advantages of operating under atmospheric pressure and requiring less sample pretreatments.However,existing methods still have shortcomings such as poor desorption effect and low sensitivity.Therefore,based on micro-fabricated glow discharge plasma desorption/ionization mass spectrometry（MFGDP-MS）,an innovative rapid detection technology for screening and quantifying OPPs in vegetables was developed by combining Fe₃O₄/ZrO₂ and temperature control system（TCS）.Meanwhile,the laboratory-made microwave-induced plasma desorption/ionization（MIPDI）technology has been explored to study the rapid degradation of triazophos.The main work and research results are as follows:（1）Based on the thermally assisted desorption of TCS and the simplified pretreatment of Fe₃O₄/ZrO₂,a rapid and trace detection method for OPPs in vegetables was established by MFGDP-MS.First,the combination of the constructed TCS and MFGDP effectively solved the problem of low desorption efficiency for OPPs.Meanwhile,Fe₃O₄/ZrO₂ was synthesized by one-step coprecipitation method,which can not only realize the specific adsorption of OPPs,but also use an external magnetic field for separation,simplifying the steps of sample preparation.Under optimized adsorption conditions and TCS temperature,the limit of detection of standard solution as low as of 0.0068-0.7500μg L^-1 mm^-2 was achieved,and the relative standard deviation was less than 17.8%,which improved the detection sensitivity.Moreover,a good recovery rate（76.9-123.5%）can be obtained by matrix spiked experiment,indicating that the combination of Fe₃O₄/ZrO₂ and TCS-MFGDP-MS can screen and quantify7 OPPs in Chinese cabbages and onions.Finally,the analytical performance of the method was evaluated by ultra-performance liquid chromatography-mass spectrometry（UPLC-MS）,and the established method was compared with other methods reported in the literature,which further confirmed the rapid and accurate characteristics,indicating that this method can realize the rapid determination of OPPs in vegetables.（2）The degradation of triazophos was investigated based on the advantages of electrodeless discharge and high desorption efficiency of new MIPDI technology.First,the influence of the operating parameters of MIPDI on the degradation of triazophos was investigated.Under the optimized parameters,the aqueous solution of triazophos can reach a degradation rate of 94.5%with 20 min,indicating that a better degradation effect could be obtained in a short time.Then,a spectrometer was used to measure the active particles in the plasma,and the?OH,?H,?O and other free radicals that played a major role in the degradation were obtained,showing that MIPDI can produce strong oxidizing active particles.A kinetic model for the degradation of triazophos by MIPDI was established,and the results showed that the degradation of triazophos in aqueous solution conformed to the first-order kinetic model.Finally,the 20 min degradation solution was detected by UPLC-MS,and the obtained spectra and degradation products were analyzed by compound discovery software,indicating that MIPDI can realize the degradation of triazophos.Based on the identification,the possible degradation pathways of triazophos were deduced,including oxidation and hydrolysis.