Study On The Resonance Light Scattering And Its Analytical Application In Ternary Ion-associated Systems

Resonance light scattering (RLS) is a new technology developed in 1990s for analysis with high sensitivity and simplicity and rapidness, which has been applied widely in the fields of life sciences, environmental sciences and the investigation of nanometer materials. However, it is rarely applied to determinate inorganic elements, especially the quantitative analysis of some trace ions in the environmental pollution and some food using the intensity of resonance light scattering enhanced by ternary ion-associated systems. As the basic theoretics of the resonance light scattering technique is still not perfect, it's necessary to do a lot of experimental and theoretical research yet. We also have done some work about it.In this dissertation, the first, the common fluorescence spectrophotometer is used to study the ion-associated systems of cadmium(II)-phenanthorline-bromophenol blue system and zinc(II)-thiocyanate- crystal violet system. Two analytical methods for determination of Cd(II)and Zn(II)have been established. They are simple, rapid and high sensitive. Then, fluorescent dye(Fluorescein) and non-fluorescent dye(Crystal violet) are analyzed based on the light scattering spectrum, fluorescence spectrum, common absorbance spectrum and light polarization techniques. We have analyzed the mechanism and essence of the spectral phenomenon of light scattering, and obtained the useful information which can provide some theory and experimental basis for their application on biochemistry, environment science etc. The main contents are described as follows:1.Resonance light scattering spectrum of cadmium(II)- phenanthorline- bromophenol blue system has been studied. The effects of interference substances and optimization of procedure have been investigated. In the presence of Tris-HCl(pH=9.60),Cd2+ reacts with Phen to form the chelate cation, which further reacts with acid dye of BPB to form an ion-associated complex. Then, the complex molecules are accumulated to particles by virtue of hydrophobic forces and other molecular forces. This results in significant enhancement of RLS intensity, and the enhanced intensity of RLS at 638nm is proportional to the concentration of Cd²⁺. The linear range is 0-3.20mg/L with a correlation coefficient of 0.9985.The detection limit is 4.5ug/L. Thus a new analytical method for determination of Cd²⁺ has been established. It has been applied to the determination of Cd2+ in mixed samples and environmental water with satisfactory results.2.Resonance light scattering spectrum of zinc(II)-thiocyanate- crystal violet system has been studied. The spectral characteristics, the effect factors and optional conditions of the ion-association reaction have been investigated. Zn²⁺ reacts with SCN- to form the combined anion, which further reacts with CV+ which is the existing form of alkaline dye of CV in acid solution to form an ion-associated complex. Then, the complex molecules are accumulated to particles by virtue of hydrophobic forces and other molecular forces. It's found the RLS intensity of the system has significant enhancement at 334nm, and the enhanced intensity of RLS is proportional to the concentration of Zn²⁺ .The linear range is 64ug/L-1920ug/L with a correlation coefficient of 0.9989.The detection limit is 0.62ug/L.Thus a new analytical method for determination of Zn²⁺ has been established. It has been applied to the determination of Zn²⁺ in power milks with satisfactory results.3.We have studied mechanism and influence factors of resonance light scattering spectra of fluorescein(Flu) in detail. In neutral and alkaline solutions, the RLS intensity of Flu is enhanced significantly. It's found that the RLS, fluorescence and absorption spectra are the same tendency on intensity and the change of wavelength with the increase in pH. The fluorescence excitation and emission spectra of Flu overlap partly, and the RLS peak lies between the fluorescence and emission peaks. In light polarization experiment, the polarization of Flu is measured to be P≈0.020.We also investigate the changes of RLS spectra and fluorescence spectra when the concentration of Flu solution increases in strong alkaline solution. It also indicates the two spectra are connected closely. All the above experimental facts reveal that the RLS of Flu is resonance fluorescence.4.Mechanism and influence factors of resonance light scattering spectra of crystal violet (CV) aqueous solution are studied. The intensity of RLS of CV increases with an increase in pH before pH =11.It comes to the strongest when the pH =11.Then it keeps steady. Acidity of the solutions influences the acid-base equilibrium of CV and its existing state. The inherence result of the enhance of RLS is the forming of molecule congeries. We also find the spectral feature of RLS is related to the absorption spectra of CV. By a light polarization experiment, the RLS of CV is demonstrated to be polarized light basically.This dissertation conducts experimental research and theoretical discussion on the mechanism of the increase of resonance light. It also develops two new methods of RLS spectra for determination of Cd2+ in the environmental pollution and Zn2+ in power milks. The methods developed in this research enjoy high sensitivity, simplicity, speed and low cost, therefore, have practical significance in application.