Applications Of Several Nanomaterials In Pesticide Residue And Organic Contaminant Analysis

The analysis of pesticides and organic contaminants in food and environmental samples has received increasing attention due to their potential harm to humans and other creatures.Because of the complexity of matrix,a pretreatment step is imperative for purifying and enrichment.The existing methods of sample pretreatment and detection are usually of high cost and need the professional operation.Therefore,the development of simple,fast,cheap extraction method and testing method is of great importance.Nanomaterials have been become the focus of attention due to their unique structure,large ratio surface area,and optical properties.Graphene is a novel class of carbon nanostructures which possess an ultra-high specific surface area.Graphene was evaluated as a cleanup adsorbent for GC-MS analysis of 17 pesticides in carrot,grape,tomato and rape with the QuEChERS method.The recoveries were 92-120%.Comparative studies showed graphene has better cleanup ability than commonly used graphitized carbon black(GCB).Besides cleanup,graphene was also explored as an adsorbent for efficient extraction of 15 phthalate acid esters(PAEs)from different water matrixes(ultrapure water,river,and sea).A simple and inexpensive dispersive solid-phase extraction was established for extraction and followed by GC-MS analysis.The extraction conditions such as the amount of graphene,the desorption solvent,adsorption time,desorption time and the solution pH were optimized.The recoveries of PAEs were between 71-117%.Finally,the method was applied for the determination of PAEs in environmental water samples in China.MnO2 nanosheets are promising nano quenchers due to their wide absorption band,and excellent light absorption capacity.The fluorescence emission of fluorescein-5-isothiocyanate(FITC)was effectively quenched by Mn02 and reversed H2O2.A MnO2-FITC fluorescence assay for sensitive detection of organophosphorus pesticides(OPs)based on the enzymatic conversion(ACh by AChE and ChOx to form H2O2)was proposed.LOD of this sensing platform for the determination of paraoxon was 1 ?g L-1.The recoveries of paraoxon in tap and river water were 89-108%.Carbon quantum dots(CQDs)have the desired advantages of low toxicity and good biocompatibility.The fluorescence emission of CQDs can be effectively quenched by Au NPs via fluorescence resonance energy transfer(FRET).Thiocholine,which was produced from acetylthiocholine(ATC)by the hydrolysis of butyrylcholinesterase(BChE),could cause the aggregation of Au NPs and the corresponding recovery of fluorescence emission.The catalytic activity of BChE could be irreversibly inhibited by OPs and a FRET-based sensing platform for OPs determination was established.Paraoxon was studied as an example of OPs.LOD of this method was 0.05 ?g L-1.The recoveries of paraoxon in tap and river water were 90-103%.This thesis shows that nanomaterials can be applied for sample pretreatment,including purifying and extraction,and OPs detection.