A Novel Molecularly Imprinted Monolithic Sieve And Its Application To Analysis Of Pesticides Residues

Pesticides have played an important role in control the growth of weeds and prevent crop damage by insects. Some pesticides, even though no longer used, persist and remain in the environment. Residues of these pesticides are sometimes found on food due to the contaminated soil or waters. The risk on human health from exposure to pesticides will be accumulated via food chain. The hygienic standards of our country and European Union (EU) legislation and United States Environmental Protection Agency (EPA) have strict established a maximum herbicides residues level in the drinking water. Recently, more and more attentions are paid to drinking water and pesticide residues analysis. Pesticide residues limit of foreign countries on China’s exports of agricultural products become restricter. The key of the drinking water is setup a rapid and accurate pesticide residue analysis method. Commonly, pesticide residue analysis includes two steps: pretreatment and determination. Of which, due to the complexity of sample matrix and the serious interference of other compositions, sample pretreatment is one critial step piror to the chromatographic analysis. Sample preparation is one of the most important factors that affect the accuracy of analytical result; at the same time, it is the most consuming-time step in the whole procedure.The procedure of sample preparation includes extraction, purify, concentrating and other steps. In recent years, some novel sample preparation methods is proved to be a rapid analytical technique and can be widely used in environmental, biological, chemical, medical and other aspects. Sample preparation has developed and sorted into several different models including solid phase extraction, solid phase microextraction (SPME), supercritical fluid extraction and so on. Additionally, the SPME method has been developed and sorted into several different models including in-tube solid phase microextraction, membrane extraction, stir-bar sorptive extraction and so on. A novel solid phase microextraction method have been established which based-on molecularly imprinted monolith (MIP-SPME). Comprehensive attention has been paid to the development and application of MIP-SPME.Molecular imprinting is a novel biometic technique which is used to prepare molecularly imprinted polymers with high ability to identify target molecular. The molecularly imprinted polymer is based on the in situ co-polymerization of cross-linkers and functional monomers that form complexes with template molecules prior to polymerized material. MIPs have features of specific selectivity, easy to operation, environmentally and stability to provide an effective way to separate and remove trace-level organic compounds in the environment. MIP-SPME is the most common sample preparation method and it combines sampling, isolation, enrichment in one step.In this paper, two molecularly imprinted monolithic materiasl were prepared as the extraction medium and combined with high-performance liquid chromatography. Their application for determination and analysis pesticide residues (flumetsulam, triazine herbicide) in water samples were studied. The MIPs is a very suitable material for SPME method because of simplicity, ease of operation, reliability, accuracy, reproduction. The combination of molecular imprinting and SPME methods would perfectly provide a powerful pesticide residue analytical method. The main research works are as follows:1. A novel solid-phase microextraction method based-on moleculary imprinted monolithic sieve (MIP-sieve) was developed with flumetsulam as the template molecule,the sample preparation method was coupled with high-performance liquid chromatography(HPLC) for the analysis of flumetsulam in environmental water samples. In this work, the polymer monolith was synthesized within the channels and the macropores (dp-20μm) of porous polypropylene sieve. The characteristics and application of the MIP-sieve were investigated. The optimized polymerization conditions、extraction conditions and desorption conditions were studied. The method was applied to flumetsulam determination in the spiked water. Satisfactory recoveries (79.7%-98.7%) and good repeatability (RSD5.4-10.7%, n=5) were obtained. The proposed MIP-SPME method has been proved as an attractive alternative sample preparation method due to its simplicity, ease to operation, selectivity and environment-friendly.2. A propazine molecularly imprinted polymer (MIP) monolithic sieve was fabricated as new solid-phase microextraction sorbent, a SPME method base on the novel material was coupled with high-performance liquid chromatography for analysis of triazine herbicides. The characteristics this MIP-sieve were investigated. In the experiment, porogen type, extraction temperature and time, desorption time and temperature, and other conditions were studied. In the optimzed conditions, good reproducibility (RSD<12.6%), higher sensitivity (LOD<34.3ng mL-1), wider linear range (0.05-5.0μg mL-1) were obtained. The MIP-sieves are suitable for the selective extraction of trace triazines in water sample, tea sample and other complicated samples.