Study On The Preparation Of Novel Porous Extraction Sorbents And Its Application In Environmental Monitoring And Food Analysis

Sorbent-based extraction is one of the most significant methods in sample pretreatment. Developing economic extraction sorbents with high sorption capacity, and exploiting suitable extraction formats are two hot spots in this field. Organic porous monoliths possess many advantages such as ease of preparation, large specific surface area, fast mass transfer velocity and versatile surface chemistry. Therefore, porous monoliths possess great application prospect in the field of sample pretreatment.Except for high performance sorbents, suitable extraction formats are needed in order to realize the effective extraction of target analytes. Among present extraction formats, stir cake sorptive extraction (SCSE) integrates extraction, purification and enrichment into a single step. Besides, it is convenient, environmentally friendly and excellent longevity. Substrateless fiber based solid phase microextraction (SLFBSPME) is another extraction formats with many advantages such as simplicity of coating process, and good life span. Previous researches have demonstrated that above mentioned extraction formats contained tremendous application potentials. Therefore, in this research, several novel porous sorbents were prepared, and acted as the extraction media of SCSE and SLFBSPME. At the same time, fast and sensitive analytical methods for phenols, benzimidazoles in water samples and parabens, Sudan dyes in food samples were developed by combining with high performance liquid chromatography/diode array detector (HPLC/DAD). The main studies are as follows:1. Using allylthiourea and divinylbenzene as functional monomer and crosslinker, respectively, a new stir cake sorptive exraction sorbent based on Poly(allylthiourea-co-divinylbenzene)(SCSE-ATDB) monolith was synthesized. The influence of the contents of monomer, crosslinker and porogen on extraction performance was investigated thoroughly. The monolithic material was characterized by several techniques, such as elemental analysis, infrared spectroscopy, scanning electron microscopy and mercury intrusion porosimetry. At the same time, several extraction conditions such as extraction and desorption time, pH value and ionic strength in sample matrix were optimized. Under the optimum conditions, a sensitive method to detect trace phenols in water samples was established by combining SCSE-ATDB and HPLC/DAD. Results show that low detection (LOD, S/N=3) and quantification (LOQ, S/N=10) limits were achieved for the phenols, within the ranges of0.18μg/L-0.90μg/L and0.59-2.97μg/L, respectively. Finally, the proposed method was successfully applied to the determination of phenols in three environmental water samples, with acceptable recoveries and satisfactory repeatability.2. A new polymeric ionic liquid monolith material was prepared and used as sorbent of SCSE (SCSE-PILM). The SCSE-PILM was in-situ synthesized using1-vinylbenzyl-3-methylimidazolium chloride, divinylbenzene as monomer and crosslinker, respectively. Because there were abundant functional groups in the sorbent, it could offer multi-interaction modes. The results demonstrated that SCSE-PILM could not only extract polar compounds such as aromatic amines by hydrogen-bonding, dipole-dipole and π-π interactions, but also enrich apolar compounds such as parabens through π-π and hydrophobic interactions. Furthermore, it also has extraction capacity for inorganic anions. At the same time, a sensitive analytical method of parabens in fruit juice and soy sauce samples was established, and the linear ranges of PBs were2.0μg/L-200.0μg/L; LOD and LOQ were0.11μg/L-0.33μu.g/L and0.37μ.g/L-1.10μg/L, respectively; the recoveries for parabens in real samples were61.2%-103.0%; the intra-and inter-day precisions with relative standard deviations (RSDs) were all below11%; the results show that the method has good practicability.3. In order to effectively extract benzimidazole residues in water, milk and honey samples, Poly(1-allyl-3-methylimidazolium bis-[(trifluoromethyl)sulfonyl] imide-co-divinylbenzene) monolith was prepared and used as extraction medium of SCSE (SCSE-AMMDB). The preparation and extraction conditions were optimized in detail. After that, a simple and effective method for the determination of trace benzimidazole residues in water, milk and honey samples was established by coupling SCSE-AMMDB with HPLC/DAD. The results indicated that the LODs and LOQs for target compounds were0.020μg/L-0.100μg/L and0.068μg/L-0.340μg/L. Recoveries obtained for the determination of benzimidazole anthelmintics in spiked samples ranged from70.2%to115.0%. The method shows good reproducibility, LODs and LOQs for benzimidazoles were far below maximum residue limits (MRLs). Therefore, the proposed method is able to meet the demands of the determination of benzimidazole anthelmintics in milk, honey, and water samples.4. To increase the extraction speed, a novel extraction format termed substrateless fiber based solid phase microextraction (SLFBSPME) was introduced and applied for sample pretreatment. Vinylimidazole and octadecyl methacrylate were used as mixture monomers to prepare Poly(vinylimidazole-co-octadecyl methacrylate-co-divinylbenzene) porous monolith. Sudan dyes were selected as target analytes to investigate the effect of preparation and extraction parameters on extraction efficiencies. Afterwards, a practicable and effective method to detect sudan dyes in ketchup and duck yolk samples was developed by coupling SLFBSPME with HPLC/DAD. The LODs and LOQs were0.14μg/L-2.17μg/L and0.45μg/L-7.17μg/L, respectively; recoveries obtained for sudan dyes in spiked samples ranged from60.8%-120.2%. The developed method shows wide linear ranges, acceptable recoveries, good accuracy and reproducibility. At the same time, SLFBSPME exhibited some advantages such as simplicity, fast extraction speed, good reproducibility and environmentally friendly, Therefore, it is an extraction format with great application prospect.