Research On New Analytical Methods For Determination Of Fipronil And Its Metabolites

Fipronil,as a broad-spectrum insecticide of phenylpyrazole,is mainly used to control various types of insects in agricultural production,animal husbandry,public health,storage supplies etc.by right of its merits such as high insecticidal activity and low toxicity to mammals.However,some studies had shown that fipronil exhibited high toxicity and disadvantageous impacts on non-target organisms,such as butterflies,bees,dragonflies and many aquatic organisms,and its exposure also posed a safety hazard to human health.Furthermore,fipronil can be degraded into three metabolites including fipronil desulfinyl,fipronil sulfide and fipronil sulfone through photolysis,reduction and oxidation under natural conditions.These substances are more active and toxic for mammals,and easily combined with lipid-rich tissues,then bioaccumulate through the food chain,posing a huge threat to the health of the population.Consequently,it is of great significance to establish a stable and reliable method to monitor fipronil and its relative metabolites in different samples.In this dissertation,the author is devoted to the fabrication of novel separation materials and the development of novel sample preparation methods for the efficient separation and enrichment of trace amounts of fipronil and its metabolites in different samples.This study provides new ideas and directions for the analysis and determination of fipronil and its metabolites,and provides technical support for the establishment of relevant limit standards for fipronil and its metabolites.The major contents of this dissertation are described as follows:(1)The overview of fipronil and its metabolites was briefly introduced.The focus was to review the pretreatment technology for determination of fipronil and its metabolites in different sample matrices.(2)A new method for the determination of fipronil and its three metabolites in environmental water samples was developed based on meltblown nonwoven fabric solidphase extraction(SPE)combining with gas chromatography-electron capture detection(GC-ECD).This method used the meltblown nonwoven fabric in the medical surgical mask as the sorbent to prepare the meltblown SPE cartridge.The target analytes were retained on the SPE cartridge through hydrophobic interaction,and then desorbed with a mixed solvent of acetone and ethyl acetate(7:3,V/V).This method was successfully applied in the analysis of fipronil and its three metabolites in various types of water samples.It has the advantages of less usage of organic reagents,simple and quick operation,low analysis cost and environment-friend,which provides a new idea for the determination of hydrophobic substances in the environment samples.(3)A new method for separation and enrichment of fipronil and its metabolites in eggs was proposed by combining a modified QuEChERS procedure with a disposable polyethylene pipet assisted DLLME(DPP-DLLME).The DPP-DLLME employed low density solvent as extractant and was conducted in a cheap,disposable polyethylene pipet with an open and narrow tip upside.After the phase separation,the extractant was separated and concentrated in the narrow neck of the pipet,which could be directly withdrawn by a microsyringe for instrument analysis.By coupling with gas chromatography-mass spectrometry(GC-MS)detection,a rapid and sensitive method for the determination of fipronil and its metabolites in eggs was established.This method has the advantages of high sensitivity,simple operation,small sampling volume,low toxicity of reagents and low dosage,etc..It has great application potential in routine analysis.At the same time,it provides a new direction for separation and enrichment of pesticide residues in complex food matrices.(4)A new method for the determination of fipronil and its three metabolites in edible oils was established based on pollen grains solid-phase extraction combining with GCECD.In the experiment,natural pine pollen was used as the sorbent to prepare pollen SPE cartridges,and fipronil and its metabolites were selectively separated and enriched from edible oil based on hydrogen bond interactions.As a natural material,pollen grains present well absorption capacity for some polar compounds due to their special functional structures.Their stable composition and appropriate particle size(about 40 μm)also make them suitable for SPE.After exposed the active groups,pollen grains can be directly used as the sorbent for the separation and enrichment of fipronil and its metabolites from edible oils.The method was successfully applied to detect fipronil and its metabolites in several oil samples with different brands from local market.The result proved that this method has good practical application potential in sample pretreatment.