| Compared with traditional sample preparation method, microwave-assisted sample preparation method can accelerate the extraction process with less reagent consumption and high-level automation, and it is prone to couple with other sample pretreatment techniques and be widely used in pre-processing of environment analysis. As reported in the literature, microwave-assisted continuous leaching has been developed to leach heavy metals from leaves and soils with dilute nitric acidused as leaching agent and-the microwave-assisted leaching technology shortens the sample preparing time and simplifies the operation steps. But it has the drawback of relatively low sampling throughput compared with high-pressure microwave-assisted digestion (MAD) technique, and that limits its use.In this thesis, we have expanded the application of dynamic microwave assisted extraction (DMAE) device in our laboratory, we apply sieve plates into the sample cell and make it suitable for acid-leaching system as well as soil sample of small particle size. Firstly, we use the dynamic microwave-assisted leaching (DMAL) technology to leach heavy metals in soil, and subsequently it was combined with other sample pretreatment techniques for the extraction of tetrabromobisphenol A (TBBPA) in soil.Specific contents are as follows:l.In this work, a multi-throughput dynamic microwave-assisted leaching (MTDMAL) method was developed to the leaching of Cu, Mn, Zn and Pb in soils, which combined the advantages of microwave and dynamic leaching technique with five soil samples treated simultaneously. The MTDMAL method has been successfully applied Soil was leached with dilute nitric acid (20%, w/w) under microwave power of 375 W, and the collected volume of 20 mL can be completed in 20 min, the leachate was diluted and centrifugated before ICP-AES detection without tedious acid evaporation, transfer and filtration steps. Experimental results are compatible with the results of the conventional method.2. In this work, a high-throughput DMAE method combined with liquid-liquid extraction (LLE) was developed to the extraction of TBBPA in soils. Weak-polar solvent was used as extraction agent and graphite powder used as the microwave absorption medium for heating the extraction solvent, and sodium hydroxide solution was used to purify and transfer target compounds in LLE. Firstly, TBBPA was extracted with 10 mL MTBE/DCM (1:1, v/v) under microwave power of 375 W for 10 min, after that,2.0 mL 2M aqueous sodium hydroxide solution was used for LLE, the solution was acidified to pH=1～2 and 2.0 mL methyl tert-butyl ether was added for another extraction. At last the MTBE phase was dried with nitrogen and the residues was redissolved with 0.5 mL methanol for high performance liquid chromatography-mass spectrometry/mass spectrometry (HPLC-MS/MS) analysis. The detection limit of the method was 1.4 ng g-1. The recoveries were in the range of 80.4%-95.1%and the precision was between 5.2%～6.9%. The method was applied to the analysis of TBBPA in soil samples with satisfactory results.3. A high-throughput DMAE method combined with solid phase extraction (SPE) was developed for the HPLC-MS/MS determination of TBBPA in soils. Briefly, TBBPA was extracted from soil with 8 mL methanol under the microwave power of 375 W and the obtained extract was diluted to 20 mL with ultrapure water and loaded on C18 SPE. Subsequently, TBBPA was eluted by 2.0 mL ethanol and determined by HPLC-MS/MS. The detection limit of the method was 1.5 ng g-1. The recoveries were 78.5%-109%and the precision was between 4.6%-7.9%. Comparing to traditional methods, the proposed approach was environmentally-friendly, the experimental process was simple and fast with 20 samples treated simultaneously. |
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