Carbon Nanomaterials-reinforced Hollow Fiber Liquid Phase Microextraction Combined With High Performance Liquid Chromatography For The Determination Of Some Organic Pollutants In Food Samples

Liquid phase microextraction (LPME), introduced in the1990s, was a miniaturizedformat of liquid liquid extraction (LLE). LPME has the advantages of simple experimentalmanipulations and requiring low amount of organic solvent. So far, as one of the mainforms of the LPME techniques, hollow fiber-based LPME (HF-LPME) has shown someoutstanding features in its application for real sample analysis, including the simple andexperimental setup and low cost. Besides, the technique shows an excellent clean-upperformance especially for the analysis of samples with complex matrix. To enlarge itsapplication scope for the trace analysis of more organic pollutants, it is desirable toimprove the sensitivity of HF-LPME.In this paper, carbon nanomaterials, including graphene (G), octadecyl modifiedgraphene (G-C18) and ordered porous carbon (OPC) were for the first time, introducedinto HF-LPME for developing carbon nanomaterials-reinforced HF-LPME system. Due tothe strong adsorbability of carbon nanomaterials for some organic compounds, theextraction efficiency of the system could be further improved. The applicability of carbonnanomaterials (G, G-C18and OPC)-reinforced HF-LPME was evaluated for the extractionand preconcentration of some organic pollutants in bottled juice, vegetables, honey andwater samples prior to their determination by high performance liquid chromatography(HPLC). The main content in this thesis is as follows:1. Graphene could improve the extraction performances of HF-LPME when it wasintroduced into the acceptor phase of HF-LPME. A new analytical method bygraphene-reinforced HF-LPME (G-HF-LPME) combined with high performance liquidchromatography-fluorescence detection (HPLC-FLD) was developed for the determinationof bisphenol A (BPA) and4-tert-butylphenol (t-BP) in bottled juices. Several importantexperimental parameters, including the type of the organic extraction solvent, theconcentration of graphene in the acceptor phase, fiber length, stirring rate, extraction time,the pH of the sample solution and ionic strength, were studied to get optimal extractionconditions for the analytes. Under the optimized conditions, the method showed a goodperformance having a linear response in the range from0.05to10.0ng/mL with the correlation coefficients of0.9965-0.9994and limits of detection (LODs, S/N=3) of0.01ng/mL. The relative standard deviations (RSDs) were in the range from6.4%to7.2%atthe spiked concentration of1.0ng/mL. The method could combine the high adsorptioncapacity of graphene and the excellent clean-up performance of HF-LPME and wassuccessfully applied for the determination of the analytes in bottled juice samples.2. A novel adsorbent, octadecyl modified graphene (G-C18) was prepared andintroduced into HF-LPME (HF-LPME) to reinforce its extraction efficiency. TheG-C18-reinforced HF-LPME was applied for the extraction of the four carbamatepesticides (metolcarb, carbaryl, isoprocarb and diethofencarb) in vegetable samples prior totheir determination by HPLC-diode array detection (HPLC-DAD). The optimization ofseveral important experimental variables was carried out in order to achieve the bestextraction efficiency. Under the optimized conditions, the calibration curve was linear inthe range of1.0-100.0ng/g for carbaryl and2.0-100.0ng/g for the other three analytes,with the correlation coefficients of0.9961-0.9994. The LODs (S/N=3) for the carbamatesranged from0.2to0.6ng/g. The recoveries of the analytes ranged from90.3%to107.4%.3. G-C18was used as adsorbent in HF-LPME for the extraction of chlorophenols inhoney samples. The linearity was observed in the range of5.0-200.0ng/g for2-chlorophenol and3-chlorophenol, and2.0-200.0ng/g for2,3-dichlorophenol and3,4-dichlorophenol, respectively. The LODs (S/N=3) of the method were lower than1.5ng/g. The recoveries of the method were between88%and108%. The method is simple,sensitive and can be applied to the analysis of chlorophenols in honey samples.4. Ordered porous carbon (OPC) was synthesized and introduced into HF-LPME toextract some phenylurea herbicides (chlortoluron, isoproturon, monolinuron and buturon)from river water and soil samples followed by HPLC analysis. The main parameters thataffect the extraction efficiency for the phenylurea herbicides were investigated. Under theoptimum conditions, the linearity was observed in the range of0.3-100.0ng/mL for riverwater sample and5.0-300.0ng/g for soil sample for buturon, and in the range of0.2-100.0ng/mL for river water sample and2.0-300.0ng/g for soil sample for the other threeanalytes. The LODs (S/N=3) of the method ranged from0.05to0.1ng/mL for river watersample and0.5to1.0ng/g for soil sample. The results indicated that the developed methodis sensitive and efficient for the determination of phenylurea herbicides in river water andsoil samples.