Dissertation > Environmental science, safety science > Environmental Quality Assessment and Environmental Monitoring > Environmental monitoring > Soil monitoring

Study on Analysis Method of Polychlorinated Biphenyls in Soil

Author ZhaoShiYan
Tutor CuiZhaoJie
School Shandong University
Course Environmental Science
Keywords Soil Dioxin- like PCBs Analysis Method GC-ECD Double column
CLC X833
Type Master's thesis
Year 2007
Downloads 707
Quotes 5
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In this thesis, a comprehensive overview of the soil environment on the basis of the pre-treatment of polychlorinated biphenyls (PCBs) and analytical methods, choose a highly toxic of 12 dioxin-like PCBs as a research object, the system of the soil environment dioxin like PCBs sample pre-treatment technology, the establishment of the separation of double-column gas chromatography (GC-ECD) qualitative and quantitative methods, and the use of established methods of analysis and the actual determination of the 12 types of dioxin-like PCBs in the soil environment, further validation of The feasibility of the method. Therefore, the study has a very important value. The main research contents and results, including the following sections: (1) the soil environment PCBs extraction method. Paper selection the environmentally friendly supercritical CO of 2 fluid extraction technology (SFE-CO 2 ) of 12 dioxin-like PCBs in the soil samples in the extraction system research and to optimize the extraction pressure, temperature, amount of modifier, of CO 2 dosage, collection of factors such as type of solvent extraction efficiency, SFE-CO 2 extraction soil samples of 12 dioxin-like PCBs. The results showed that the optimum extraction conditions, the 12 types of dioxin-like PCBs recoveries ranged from 73.0% to 129.0%, the relative standard deviation (RSD) of 1.0% to 10.5%. By the the supercritical CO 2 fluid extraction device to improve the soil samples by accelerated solvent extraction (ASE) and ASE extraction conditions were optimized. The results showed that, under the optimum extraction conditions of pressure 10 MPa, temperature 100 ° C, the extraction time 15min, the extraction solvent of n-hexane / acetone (v / v = 1/1), the amount of extracted sample 3g, 12 types of dioxin-like PCBs plus The recoveries ranged from 88.5% to 109.8%, the relative standard deviation of 1.1% to 6.7%, the recovery and reproducibility of the method are good. The paper also extraction conditions on ultrasonic extraction system optimization study, and the effects of the extraction recovery of acid-base treatment of PCBs. The results showed that ultrasonic extraction, the optimum extraction conditions: extraction solvent n-hexane, the sample soaking time 4h, ultrasonic extraction time 5 min (repeated three times), this condition of 12 dioxin-like PCBs recoveries were 93.1 % to 112.9%, the relative standard deviation of 1.1% to 10.1%. For acid-base processing, ambient temperature and pressure, concentrated sulfuric acid pickling and NaOH alkaline cleaning BE LIABLE class dioxin-like PCBs serious damage, 12 types of dioxin-like PCBs sample recoveries were 88.0% ~ 112.8 % and 83.2% to 106.5%; ultrasonic extraction conditions of 12 dioxin-like PCBs sample recovery rate of only 4.6% to 49.5% and 1.3% to 16.9%. This shows that the role of energy in the ultrasonic the structure destructive causes of concentrated sulfuric acid and NaOH PCBs enhanced, leaving the lower recovery and NaOH destructive than the PCBs destructive of concentrated sulfuric acid to PCBs. Paper supercritical fluid extraction, pressurized solvent extraction, ultrasonic extraction and Soxhlet extraction (see EPA Method 8280) four pretreatment methods from the extraction recovery, precision, equipment operation and other aspects of the comparative analysis of the system will eventually pressurized liquid extraction and the best extraction method given as a member of the paper. (2) PCBs in the soil sample extract purification method. This thesis, homemade silica gel, activated carbon column and multi-stage silica gel column sample purification technology, the study compared the effect of the different eluent PCBs elution, found that the silica gel column with 100 ml of petroleum ether / dichloromethane (v / v = 4/1) for elution allows elution highest efficiency of 94.0%; enable the highest elution efficiency was 83.7% for the activated carbon column, elution was carried out with 200 ml of n-hexane; multistage silica gel column with 150mL of petroleum ether / dichloromethane (v / v = 97/3), elution was carried out enables the highest elution efficiency was 81.5%. Purifying effect by comparing the three pillars and the eluent volume, silica gel purification techniques to determine the present study the final purification method. (3) the PCBs analysis of the soil environment. This thesis through the gas column system selection, optimization of the operating conditions of the gas chromatography, and create a double-column separation and detection methods of qualitative and quantitative analysis by GC-ECD method of analysis of the 12 types of dioxin-like PCBs in the soil environment, the effective separation of PCBs in environmental samples, laid the foundation for the development of analytical methods. Analysis system established by GC-ECD double-column separation standard stock solution containing 12 types of dioxin-like PCBs, IUPAC No. marked peaks in the resulting spectra. Identified PCBs column RTX-1701 and RTX-5 on the detection limits were 0.8 to 1.6pg and 0.9 to 1.4pg; repeated by GC-ECD analysis of 12 types of dioxin-like PCBs mixed standard in column RTX -1701 and Rtx-5 on the relative standard deviation of 2.4% to 4.3% and 2.3% to 4.3%, indicating that the experimental precision instrument high and low limits of detection, analysis of PCBs mixed standard samples and soil spiked samples, separation effects are good. (4) the determination of PCBs in soil samples using the established methods of pre-treatment and analysis methods Jinan soil samples of the three sampling points actually measured, the results were not detected in the soil of Shandong University, School of Environmental Science and Engineering behind the main building dioxin, PCBs, which may be related to near the sampling point no specific sources of pollution-related; 5 types of dioxin-like PCBs detected in Jinan Yin chenzhuang wheat field soil content of 37 to 195pg / g; roadside soil in Jinan Iron and Steel factory gate were 8 types of dioxin-like PCBs content of 50 to 671pg / g. Show that the different parts of the the soil dioxin-like PCBs pollution levels. Quality control throughout the experiment, the results showed that 12 types of dioxin-like PCBs in the RTX-1701 column average recovery was 78.1% to 95.9%, and the relative standard deviation was 2.0% to 5.6%; in RTX-5 column The average recovery of 77.6% to 97.2%, and the relative standard deviation of 2.2% to 5.5%. Show that the average recovery of 12 types of dioxin-like PCBs have reached the U.S. EPA's quality control requirements, better reproducibility of the method, created by pre-treatment methods and analysis method is feasible. In short, the paper has established two columns separated by gas chromatography (GC-ECD) qualitative and quantitative methods, laid the theoretical foundation for the effective separation of PCBs in environmental samples; PCBs in the soil environment analysis method for determining the soil environment PCBs residue levels and environmental behavior (transport, transformation and fate) study provides a method basis. Extraction of PCBs in the soil environment created by the papers - clean - separation and analysis method is an efficient, fast, reliable, low pollution characteristics, promote the use of monitoring and analysis of PCBs in other environmental solid samples can also be applied to the environment pollution The object of analysis. Therefore, this thesis has high theoretical and practical value.

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