Application Of Novel Polymer Monolith Microextraction Technique For The Analysis Of Pesticide Residues

Due to the complexity of fruit juice and environmental water samples, the concentration of the target analyte in the sample is usually minor or trace concentration levels。The purpose of sample preparation is to extraction and concentrate the target analytes from the complex sample matrix, thus reducing or eliminating the interferences of impurity in the sample to achieve the determination of analytes at trace levels. In recent years, with the development of chemical analysis techniques, sample pretreatment technology has been developing rapidly. Solid phase microextraction was developed in the early1990s. It is a extraction technique that incorporates sample extraction, purification and concentration into a single procedure. So, it has good development prospects.SPME techniques include in-tube solid phase microextraction, stir bar sorptive extraction, and so on. Polymer monolith microextraction (PMME) is a new sample preparation technique which is developed on the basis of in-tube solid phase microextraction. Similar to the in-tube solid phase microextraction, PMME incorporates sample extraction, purification and concentration into a single procedure. Molecular imprinting is a new technology developed in recent years. It has high affinity and specific recognition performance for a particular compound (template molecule). Because of the advantages of high selectivity, simple preparation, good stability, long life and so on, Molecularly imprinted technology has been used in the separation of enantiomers, drug analysis, chromatographic analysis and other aspects. Molecularly imprinted polymer monolith microextraction not only has MIP’s high selectivity, but also has PMME’s good permeability and low pressure drop advantages which is a high recognized and environmentally friendly sample pretreatment technique.In this work, two modes of SPME including molecular imprinted polymer monolith microextraction (MIPMME) and nano enhanced polymer monolith microextraction (PMME) in combination with high-performance liquid chromatography (HPLC) were used for the residue detection of certain pesticides in real samples. The main contents are listed as followings:1. An difenoconazole molecularly imprinted monolith was in situ prepared in a micropipette tip. Then, molecularly imprinted polymer monolith microextraction coupled with HPLC was used for the detection of difenoconazole in tap water and juice samples. In order to obtain the best extraction efficiency, several parameters affecting extraction efficiency such as sample flow rate, sample volume, eluent type, eluent volume and the eluent flow rate were investigated. Under the optimized conditions, the limits of detection (LODs) and the limit of quantification (LOQs), based on signal-to-noise ratios (S/N) of3and10, were0.5μg L-1and1.7μg L-1respectively. The recoveries of difenoconazole in the spiked tap water and grape juice were in the range of89.3-95.4%and87.6-92.8%, respectively. The method was effective and reliable for determination of difenoconazole in tap water and grape jucie samples2. An methomyl molecularly imprinted monolith was in situ prepared in a micropipette tip. Then, molecularly imprinted polymer monolith microextraction coupled with HPLC was used for the detection of methomyl in environmental water samples. In order to obtain the best extraction efficiency, several parameters affecting extraction efficiency such as sample flow rate, sample volume, eluent type, eluent volume and the eluent flow rate were investigated. Under the optimized conditions, the limits of detection (LODs) and the limit of quantification (LOQs), based on signal-to-noise ratios (S/N) of3and10, were0.2μg L-1and0.6μg L-1respectively. The recoveries of methomyl were in the range of84.9-105.1%. The method was effective and reliable for determination of methomylin environmental water samples.3. Adding an appropriate amount of graphene oxide(GO) in the pre-polymerization mixture, graphene oxide doped poly(MAA-EGDMA-GO) monolith was in situ prepared in a micropipette tip. And then poly(MAA-EGDMA-GO) monolith microextraction coupled with HPLC was used to determination of three carbamate pesticides in environmental water samples. Under the optimized conditions, LODs and LOQs, determined as S/N ratios of3and10, varied in the range of0.3-0.7μgL-1and1.0-2.3μgL-1, respectively. Satisfactory recoveries were obtained in the range of78.9-103.4%. The method was successfully applied to the determination of three carbamate pesticides in environmental water samples.