Electrochemically Enhanced Molecularly Imprinted Solid-phase Microextraction And Its Application

Sample pretreatment is one of the most important steps for complex sample analysis, which mainly includes sample cleanup and enrichment of target compounds. It is very important for analysis of complex samples to develop novel sample pretreatment techniques with high selectivity and extraction efficiency, and good compatibility with analytical instruments. The aim of this thesis is to develop a novel electrochemically enhanced molecular-imprinting solid-phase microextraction (EE-MISPME) for selective extraction of fluoroquinolone antibiotics (FQs) in water samples. The main contents include four chapters as following:Chapter one:Several important pretreatment techniques and analytical methods of FQs were reviewed.Chapter two:A novel molecularly imprinted polypyrrole/multi-walled carbon nanotubes (MIPPy/MWCNTs) composite coating on Pt wire was prepared and used as extraction fiber for EE-MISPME extraction. The surface structure of the fiber was characterized by scanning electron micrograph (SEM). Some parameters influencing EE-SPME extraction such as applied potential, extraction time, pH, ionic strength, and desorption solvent were optimized. EE-SPME showed good selectivity and higher extraction efficiency to FQs compared to the traditional SPME. EE-SPME coupled with HPLC to determine FQs in water samples, the limits of detection (LODs, S/N=3) for the selected FQs are1.5-5.0nmol/L. The proposed method was successfully used to the analysis of FQs spiked urine and soil samples, with recoveries of85.1-94.2%for the urine samples and89.8-95.5%for the soil samples.Chapter three:A novel molecularly imprinted mesoporous silica/muti-walled carbon nanotubes (MIMSN/MWCNT) on Ti wire was prepared and used extraction fiber for EE-MISPME extraction. Some parameters such as applied potential, extraction time, solution pH, and ionic strength were optimized. Under the optimized conditions (0.5V, pH7.21, extraction time of60min, no salt addition). EE-MISPME showed the best performance for extraction of FQs. EE-SPME coupled with HPLC-MS/MS to determine FQs in water solutions, LODs were0.22-2.04nmol/L. The proposed method was successfully used to the analysis of FQs spiked seawater samples with recoveries of89.3-95.5%. Chapter four:A novel graphene hybrid molecularly imprinted polymer monolith fiber (Gr-MIM) was prepared using bisphenol A (BPA) as template, trimethylolpropane (TRIM) as crosslinker, methacrylic acid (MAA) as functional monomer, N, N-dimethylformamide (DMF) as solvent, and azodiisobutyronitrile (AIBN) as initiator by thermal polymerization. SEM, Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis were used to characterize Gr-MIM fiber. Under the optimized conditions (pH7.23, extraction time of60min, no salt addition), the novel fiber could selectively extract BPA in water samples. Gr-MIM coupled with HPLC to determine BPA in water solutions, LOD (S/N=3) was0.15μg/L. The proposed method was successfully used to the analysis of BPA spiked seawater samples with recoveries of93.7%.