Micro-extraction Technology Based On Covalent Organic Framework And Graphene Composite For The Determination Of Organic Pollutants In Food And Cosmetics

Nowadays,with the development of food and cosmetics industry,people's living standard has been greatly improved,while there are some safety problems.For example,a variety of chemical additives were added or some chemical pollutants may produce during food production,which will cause great harm to human health.Similarly,some manufacturers adulterate some poisonous and harmful substances in order to reduce the cost of the product or improve the effective function of the product.Therefore,the toxic and harmful substances potentially harmful to human health have attracted more and more attention.However,due to the complexity of the food matrix and cosmetics matrix,there is also more interference in the detection process,so the pre-treatment of the sample is needed to be tested.Pre-treatment technique is one of the most important and critical steps in the analysis.Analytes can be isolated from the samples by sample pretreatment techniques,which can reduce or eliminate the matrix interference,at the same time,it can enrich the analyte to achieve the aim of trace analysis to the analyte concentration so as to achieve the purpose of the trace analysis.In this thesis,the solid phase microextraction technology,hollow fiber stir bar sorptive extraction and magnetic hollow fiber stir bar sorptive extraction combined with gas chromatography and liquid chromatography was established for the detection of organic pollutants in cosmetics and food.This thesis is mainly concerned with the following aspecting:?1?Headspace solid-phase microextraction?HS-SPME?coupled with gas chromatography-mass spectrometry?GC-MS?was used for the simultaneous determination of seven chlorophenols?CPs?compounds?2-chlorophenol,3-chlorophenol,4-chlorophenol,2,4-dichlorophenol,2,3-dichlorophenol,3,4-dichlorophenol and 2,4,6-trichlorophenol?from honey samples and canned yellow peach.A covalent organic framework constructed from 1,3,5-triformylphloroglucinol?Tp?and benzidine?BD?was used as the SPME fiber coating to preconcentrate the CPs acetylation derivatives.The main experimental parameters including derivatization conditions,extraction temperature,extraction time,salt addition,headspace volume and desorption temperature were investigated.The fiber had a good extraction capability for the CPs.The limits of detection?LOD?were below 0.7?g/kg for honey and 1.8?g/kg for canned yellow peach samples.There was a good linearity over the concentration range of the analytes from 2.4 to 300?g/kg with correlation coefficients higher than 0.9919.Good repeatability?<11.1%?and high recoveries?72.0%¹15%?of the analytes for the method were observed under the optimal conditions.The established method was successfully applied for the analysis of honey samples and canned yellow peach sample.?2?In this work,a zeolitic imidazolate framework based graphene oxide composite?ZIF-8@GO?was prepared and used as the adsorbent in hollow fiber stir bar sorptive extraction?HF-SBSE?.The stir bar was constructed of a small section of hollow fiber filled with 5 mg ZIF-8@GO and a thin stainless wire of 1.5 cm long in its lumen,and used to extract trace levels of phthalate esters?PAEs?from children's food samples prior to gas chromatography-mass spectrometric detection.The main experimental parameters that can impact the extraction efficiency including the extraction temperature,extraction time,stirring rate,sample salinity and desorption conditions were investigated.Under the optimized conditions,the limits of detection?LODs?for the five PAEs?diethyl phthalate,dipropyl phtalate,diisobutyl phthalate,butylbenzyl phthalate,di?2-ethylhexyl?phthalate?were 0.15⁰.6?g/L for CiCi beverage and pear juice samples with a wide linear range of0.5⁵00.0?g/L,as were as the LODs and a wide linear range of Jam sample were 0.75².2?g/kg and 2.5²000?g/kg respectively.The current method was applied successfully for the determination of the PAEs in children's food samples.The results showed that the ZIF-8@GO based hollow fiber stir bar can be reused for 120 extraction cycles without a significant loss of extraction efficiency,indicating a high durability and stability.The ZIF-8@GO showed a high adsorption for the compounds containing aromatic rings.?3?The authors describe a three-dimensional single layer graphitic carbon nitride modified graphene composite?g-C₃N₄@G?deposited on a stainless steel wire by a sol-gel technique.The coated fiber was applied to direct immersion solid-phase microextraction of trace levels of polycyclic aromatic hydrocarbons?PAHs?from cosmetics samples prior to their determination by gas chromatography with mass spectrometry?GC-MS?.Due to?stacking interaction and hydrophobic interaction between the g-C₃N₄@G coating and the analytes?naphthalene,acenaphthene,fluorene,phenanthrene,fluoranthene and pyrene?,the fiber displays an excellent adsorption capability for the analytes.Under optimized conditions,the method has a wide linear range,low LODs?from 1.0 to 2.0 ng/L?,good repeatability and high recoveries.It was successfully applied to the determination of PAHs in cosmetics.The g-C₃N₄@G fiber also exhibited good durability.?4?A magnetic hollow fiber stir bar sorptive extraction?M-HF-SBSE?method was applied for the extraction of trace levels of various chlorophenols prior to their determination by high performance liquid chromatography.The reduced graphene oxide functionalized with magnetic iron oxide nanoparticles and graphitic carbon nitride was prepared and used as adsorbent.It was characterized by scanning electron microscope,X-ray diffraction and vibrating sample magnetometer.Placed in a polypropylene hollow tube,the material was applied to the extraction of 3-chlorophenol,2,3-dichlorophenol,2,4-dichlorophenol,and 2,4,6-trichlorophenol in cosmetic samples.Several experimental parameters that affect extraction efficiency were optimized.Following desorption with alkaline methanol,the chlorophenols were quantified by high performance liquid chromatography.A linear response was observed in the 1.0²00?g/kg CPs concentration ranges.The method detection limit?at a signal-to-noise ratio of 3?range between 0.20 and0.30?g/kg.The relative recoveries of the CPs from cosmetics samples are in the range from 80.5 to 104%,with relative standard deviations of<12%.The filled extraction tube is high durable and stable.It can be used for 120 extraction cycles without a significant loss of extraction efficiency.The good adsorption ability of the sorbent was attributed to the strong?stacking interaction between the graphitic carbon nitride functionalized reduced graphene oxide and the aromatic rings in the CPs.