In Vivo Solid-phase Microextraction Technology For Monitoring The Environmental Behavior Of Pesticides In Edible Plants

Investigation of the environmental behavior of plants,such as absorption,migration,metabolism,and elimination of pesticides is greatly significant to fully identify the bioconcentration,persistence and health risks assessment of the substance.Therefore,it is vital to establish appropriate analytical methods for monitoring the environmental behavior of pesticides in edible plants.Traditional in vitro analysis is damaging or lethal to animals and plants,and it is impossible to repeated sampling and long-term monitoring of the same organism.In this paper,an in vivo solid-phase microextraction(in vivo SPME)probe with strong anti-matrix fouling,excellent biocompatibility,fast mass transfer rate,and specific recognition for non-polar halogenated organic compounds was designed and fabricated.Based on this probe,an in vivo SPME sampling method for non-polar halogenated organic pesticides in plants was established.This method combined with gas chromatographymass spectrometry(GC-MS)was developed to be a minimally invasive in vivo SPMEGC-MS analysis method,which integrates sampling,extraction,concentration,and injection.A sampling rate(SR)correction theory-based quantitative method was applied.In situ sampling,qualitative detection,and accurate quantification of pesticides and their metabolites in living plants were achieved.The environmental behaviors such as absorption,enrichment,migration,metabolism and elimination of pesticides in garlic under pesticide stress were studied.Not only evaluated the bioconcentration and persistence of pesticides,but also evaluated the edible risk of plants under drug stress,and gave suggestions on the application of plants during planting.It provides a convenient,efficient and reliable qualitative and quantitative method for the determination of foreign substances in living organisms.The specific research contents of this article are as follows:1.Multi-walled carbon nanotube/polyaniline-polypyrrole@polydimethylsiloxane(MWCNTs/PANI-PPy@PDMS)fiber was synthesized on the surface of stainless steel wire by in-situ electrodeposition and post-modification.The morphology,structure,thermal stability,enrichment effect and applicability to biological sampling of the material were investigated in detail,the parameters affecting extraction and desorption performance were optimized,and the adsorption mechanism of the material.was also explored.The experimental results indicate that the homemade fiber shows excellent extraction selectivity for non-polar halogenated organic compounds,and its enrichment ability is better than that of three commercial SPME fibers.In addition,the self-made probe possesses good thermal and mechanical stability,excellent biocompatibility and resistance to biological corrosion,and is suitable for in vivo sampling of living organisms.It provides a green,efficient,economical and fast strategy for the determination of pesticide residues in edible plants.2.An in vivo SR-SPME-GC-MS method was established for in situ sampling,qualitative and quantitative determination of insecticides in garlic.The absorption,enrichment and migration behavior of insecticides under stress,as well as the elimination behavior of insecticides after stress elimination were investigated.Garlic exhibits bioaccumulation and enrichment effects towards hexachlorobenzene,fipronil and bromofenap,but there is obvious tissue difference in the degree of enrichment for the three insecticides in the garlic.The closer to the roots,the higher the pesticide content is.Garlic shows the least resistant to chlorfenapyr.Fipronil in garlic is the most easily migrated and possesses the weakest digestion ability.It is worth to mention that insecticides with high enrichment degree or weak degradation ability should be avoided during planting garlic,such as fipronil and fipronil.The elimination of insecticides in garlic in the first 24 hours accorded with the first-order elimination kinetics,and the elimination rate was good.55.0%-80.3%residues were eliminated in garlic bulb in the first 24 h,those in garlic leaf sheath were 65.8%-73.1%.However,when the harvest interval was 4 days,garlic bulbs still had edible risk and leaf sheath had no edible risk under the pesticide stress of this dose.3.The dynamic changes,absorption,metabolic and elimination behavior of fipronil and its metabolites were investigated in garlic.Under stress,pesticides can be absorbed and accumulated quickly through the root system of garlic plants.At the same time,three metabolites of fipronil are quickly formed through photolysis,reduction and oxidation,and their contents follow the order of fipronil-sulfone>fipronil-sulfide>fipronil-desulfinyl.However,fipronil in garlic undergoes metabolic transformation mainly through oxidation and reduction reactions.The content of fipronil-desulfinyl is closely related to the light intensity,while fipronil-sulfone and fipronil-sulfide are mainly related to the concentration of fipronil in plants.After the stress was removed,the metabolites in garlic bulbs and leaf sheaths were harder to degrade than fipronil.The final degradation rate of fipronil in garlic was higher than 78.6%,while those for the three metabolites were lower than 25.1%.The residual amount of fipronil metabolites in garlic was approximately twice that of fipronil under the stress of 500?g L-1 fipronil,and the total residue of fipronil and metabolites was much higher than the maximum residue limits of fluoxitrile and metabolites in garlic regulated by China and the European Union,and there is a risk of eating.Therefore,special attention should be paid for metabolites in the determination of pesticide residues.The steady-state concentration of fipronil and its metabolites in garlic was positively correlated.with the dose of pesticide.In addition,the stress at high doses can stimulate the absorption of pesticides by the plant roots,resulting in an increase in the degree of biological enrichment of pesticides.