A Novel Graphene Oxide-based Solid-phase Microextraction Method And Its Application To The Analysis Of Pesticide Residue

Pesticides are being used to increase production and quality in crops over the past few decades. Excessive usage of pesticides contaminates the crop itself and the environment, eventually causing disease to human beings. China is one of the biggest crop product exporters in the world. Over 52% of the crop products are exported to countries like Japan, US and Europe. Food safety becomes a hot issue because it is not only concerning about consumers but also an international trade mark.The advantages of solid-phase microextraction (SPME) method include its use of little organic solvent and little sample volume, high selectivity and so on. And it has been widely applied to determine the pesticides residue in real sample. With the development of SPME, there have several different models of it, for example, fiber-solid-phase microextraction, in-tube solid-phase microextraction, stir bar sorptive extraction, monolith-solid-phase microextraction and so on.In this work, two novel sample preparation methods combined with liquid chromatography-tandem mass spectrometry were developed and applied to determine pesticides residue of the triazoles and triazines in water and fruit samples. The main study contents are as follows:graphene oxide/poly(methylacrylicacid-ethylene glycol dimethacrylate) monolithic frit was synthesized and used as the sorbent of the solid-phase microextraction (SPME) procedure, it was combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) for selective preconcentration of nine triazoles and triazines compounds from environmental water samples and fruit juice samples. The monolithic frit, was prepared with methylacrylicacid(MAA) as functional monomer, and ethylene glycol dimethacrylate(EDMA) as cross-linker. A series of parameters of the method, such as desorption solvent, sample flow rate, sample volume, and eluent flow rate were studied and optimized. The limits of detection for the nine pesticides were in the range of 0.75-7.31 ng L-1.The limits of quantitation were in the range of 2.49 to 24.36 ng L-1.Relative recoveries obtained for triazoles and triazines analysis in the real samples were higher than 73%. This method was successfully applied for determination of triazoles and triazines in aqueous samples.A graphene oxide/polydimethylsiloxane frit-based stir bar sorptive extraction method was combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) for preconcentration of seven triazoles and triazines compounds from environmental water samples and fruit juice samples. In this work, GO and PDMS as adsorbent material to preconcentrate seven triazoles and triazines. Polymerization, extraction and desorption conditions were optimized. Under the optimal conditions, a wide linear application range was obtained in the range of 0.02-80?g kg-1 for seven pesticides, and the recoveries were above 77% for the spiked samples.