Application Of Spectral Analysis Technique For The Determination Of Polychlorinated Biphenyls (PCBs)

Polychlorinated biphenyls (PCBs) are a kind of persistent organic pollutants (POPs). PCBs are not only carcinoenic, teratogenic and mutagenic, but also have the role of endocrine disruption. Thus, PCBs have an invaluable potential threat for ecological environment and human health. It is of significant value to study the interaction between spectral probes and PCBs, the quantitative analysis of PCBs with simple, high sensitivity and low detection limit are important in preliminary assessment of pollution levels, pathological analysis and clinical testing, which is helpful for the understanding of binding mode and reaction mechanism between persistent organic pollutants and spectral probes. Recently, the trace determination of PCBs has become a research hotspot of environmental science and analytical chemistry, which has attracted extensive attention.Based on the fluorescence and resonance light scattering (RLS) as the primary technique, this thesis focus on the development of new probes for polychlorinated biphenyls and to establish simple and sensitive methods for the quantitative determination of polychlorinated biphenyls with multiple techniques to study the interaction mechanism. The main conclusions are listed as follows:In the first section, we summarize the recent development of treatment technology and detection method for polychlorinated biphenyls.The progress of the characteristics and hazards of polychlorinated biphenyls is also commented.In the second section, the interaction between AgNPs and PCBs are stuied. From the research, we find that when PCBs are added to AgNPs solution, resonance light scattering of the system is significantly enhanced. Based on this, a novel resonance light scattering approach for the determination of PCBs is proposed. Under optimized conditions, there are linear relationships between the enhancing resonance light scattering intensity of the system and the concentrations of PCBs in the range of 8.0×10-8～1.0×10-6 g mL-1 for 2,4,4'-trichlorbiphenyl (PCB28),9.0×10-8～1.0×10-6 g mL-1 for 2,2',5,5'-tetrachlorbiphenyl (PCB52) and 4.0×10-8～1.0×10-6 g mL-1 for 3,3', 4,4'-tetrachlorobiphenyl (PCB77). The corresponding detection limits (S/N=3) were 2.6×10-8 g mL-1 for PCB28,3.3×10-8gmL-1 for PCB52 and 6.3×10-9g mL-1 for PCB77, respectively. The interaction mechanism is considered that the enhancement of RLS of PCBs is ascribed to the formation of AgNPs-PCBs aggregate.In the third section, the scattered light enhancing effect of the system of berberine and PCBs is studied. After the addition of PCBs to the berberine solution, the scattered light intensity of berberine-PCBs system was obviously enhanced and reached a maximum at 396nm, which indicated that there existed interacions between berberine and PCBs. In addition, the extent of scattered light enhancement depends on the structrure of PCBs in the order PCB77> PCB52. Under optimum conditions, the enhanced scattered light intensity is proportional to the concentration of PCBs in the range of 1.0×10-7-4.0×10-6 mol L-1 for PCB52,6.8×10-8～1.5×10-6 mol L－1 for PCB77. The detection limits (S/N=3) of PCB52 and PCB77 are 3.0×10-8 mol L-1 and 1.5×10-8 mol L-1, respectively.In the fourth section, we found that PCBs can enhance the fluorescence intensity of protein. Under optimum conditions, there are linear relationships between the enhancing fluorescence intensity of the system and the concentrations of PCBs in the range of 5.0×10-7～5.0×10-6 mol L-1 for PCB52,8.9×10-8～5.0×10-6 mol L-1 for PCB77. The corresponding detection limits (S/N=3) of PCB52 and PCB77 are 2.9×10-7 mol L-1, 2.6×10-8 mol L-1, respectively. Samples are satisfactorily determined. Furthermore, the fluorescence enhancement mechanism is discussed in detail. Results indicate that fluorescence enhancement of the system originates from the formation of BSA-PCBs complexes. In addition, PCBs are mainly bound to the tyrosine residues in BSA molecules.In the fifth section, it is found that PCBs have the interaction with CdTe quantum dots, resulting in strong enhanced light scattering and fiuorescecnce quenching of CdTe quantum dots. A new ratiometry of light scattering and fluorescence emission for the determination of PCBs using CdTe quantum dots as spectral probe is proposed. Under optimum conditions, the ratio vaule of light scattering intensity at 508 nm and fluorescence emission intensity at 558 is proportional to the concentration of PCBs in the range of 2.0×10-7～1.0×10-5 mol L-1 for PCB52,6.8×10-8～3.4×10-6 mol L-1 for PCB77. The detection limits (S/N=3) of PCB52 and PCB77 are 1.5×10-7mol L-1 and 2.1×10-8 mol L-1,respectively. This approach has been applied to the detection of PCB77 in synthetic sample with satisfactory results.The chief characteristics of this thesis are as follows:1. AgNPs is served as a resonance light scattering probe to determinate the trace of PCBs. This method has the advantages of high sensitivity, simple operation and good reproducibity. In addtion, the mechanism of the system is also discussed in detail.2. It is found that the resonance light scattering intensity of berberine-PCBs system is obviously enhanced after the addition of PCBs to the berberine solution.This method is simple, stable and quick.3. It is found that PCBs can enhance the fluorescence intensity of BSA molecules and provide a novel, selective and rapid fluorimetric approach for the determination of PCBs. The fluorescence enhancement mechanism is also discussed in detail.4. It is found that PCBs can significantly enhance light scattering and fluorescecnce quenching of CdTe quantum dots and provide a novel ratiometry of light scattering and fluorescence emission for the detection of PCBs. This method has been applied in the determination of PCB77 in synthetic sample and the result is satisfactory.