| Food safety is an important issue which everybody is concemed. Many factors impact the food safety, but food additive is more important. Somebody consider that food additive is the biggest menace to food safety. Therefore, it is necessary to develop new methods for the food additive analysis.Resonance Rayleigh scattering (RRS) and resonance nonlinear scattering (RNLS) are new analytical technology developed in recent ten years. For their excellence of high sensitivity, cheap instrument, simple operation and rapid analysis speed, these methods bring to more attention and interesting and have been studied widely and applied more and more. At present, these technology are mainly used to the study of biological macromolecules such as nucleic acids, proteins and saccharide. Furthermore, resonance Rayleigh scattering can be used to determination of trace metal ions, nonmetal ions, nanoparticle, some pharmaceuticals and food analysis.This dissertation has studied the applications of resonance Rayleigh scattering method in food additive analysis, l. Determination of antiagglomeration potassium ferrocyanide by resonance Rayleigh scattering (RRS) method (1) basic triaminotriphenylmethane dyes-potassium ferrocyanide systems; (2) double-charge triaminotriphenylmethane dyes-potassium ferrocyanide systems; (3) Fe(Ⅲ)-potassium ferrocyanide system; 2. Determination of esculent pigment: phloxine and erythrosin by resonance Rayleigh scattering (RRS) method (1) rhodamine 6G-erythrosine system; (2)cationic surfactants-phloxine systems; 3. Determination of nutritional fortification substances iodate and iodide by resonance Rayleigh scattering (RRS) method (1) potassium iodide-ethyl violet (EV) system; (2) [I2Br-]--xanthene dyes systems. Their RRS spectral characteristics, optimum reaction conditions, influencing factors and analytical applications have been studied. Furthermore, the reaction mechanism, the reasons of RRS enhanced and the relationship between RRS spectra and absorption spectra are discussed.The research contents are as follows:1. Determination of antiagglomeration potassium ferrocyanide by resonance Rayleigh scattering (RRS) method(1) Basic triaminotriphenylmethane dyes-potassium ferrocyanide systemsIn near neutral media, the resonance Rayleigh scattering (RRS) intensities of potassium ferrocyanide K4[Fe(CN)6] or basic triaminotriphenylmethane dyes such as ethyl violet (EV), crystal violet (CV), methyl violet (MV) are very weak. However, when [Fe(CN)6]4- combine with basic triaminotriphenylmethane dyes to form three kinds of ion-association complexes, their RRS intensities are greatly enhanced and new RRS spectra appear. These ion-association complexes have similar spectral characteristics and their maximum RRS wavelengths are all located at near 329 nm, but their sensitivities are obviously different. Among them, the sensitivity of EV system is the highest, and that of MV system is the lowest. The enhancement of RRS intensityΔ/ is proportional to the concentration of [Fe(CN)6]4-, so RRS method can be applied to the determination of potassium ferrocyanide. The detection limit (3σ) of the EV system for potassium ferrocyanide is 7.8 ng/mL. This method has a good selectivity. A sensitive, simple and quick method for the determination of trace amounts of potassium ferrocyanide with EV as a RRS probe was developed.(2) Double-charge triaminotriphenylmethane dyes-potassium ferrocyanide systemsIn pH 1.0 acidic medium, it is reported the interaction of double-charge triaminotriphenylmethane dyes such as methyl green (MEG), iodine green (IG) with potassium ferrocyanide on the RRS method. From our experiments it was discovered that methyl green (MEG), iodine green (IG) exists as a bivalent cation in pH 1.0 acidic medium, and K4[Fe(CN)6] exists as [Fe(CN)6]4-, they react with each other to form ion-association complexes by virtue of electrostatic forces and hydrophobic interaction, which results in the change of absorption and the great enhancement of resonance Rayleigh scattering (RRS) and the appearance of new RRS spectra. The former can be used to determination of K4[Fe(CN)6] by fading spectrophotometry, but its sensitivity is lower then that of RRS method. The detection limit (3σ) of RRS method for potassium ferrocyanide is 9.3 ng/mL (MeG system), 11.2 ng/mL (IG system), respectively, which is much higher than those of other methods. Therefore, the RRS method is more suitable for the determination of trace amounts of potassium ferrocyanide. (3) Fe (Ⅲ)-potassium ferrocyanide systemIt is discovered that Fe (Ⅲ) react with potassium ferrocyanide to form prussian blue, which results in the change of absorption spectrum and the great enhancement of resonance Rayleigh scattering (RRS). The maximum RRS wavelength is located at 316 nm. The sensitivity of this method is higher than some spectrophotometric methods and it is not influenced by the food colour. It is shown that this method has high sensitivity, and it is more suitable for the determination of potassium ferrocyanide in salinized food with satisfactory results.2. Determination of esculent pigment phloxine and erythrosin by resonance Rayleigh scattering (RRS) method(1) Rhodamine 6G-erythrosine systemIn the BR buffer solution, when erythrosine and rhodamine 6G react with each other to form ion-association complexes, the RRS intensity can be enhanced greatly and new RRS spectra appeared. A new method for the trace determination of erythrosine with RRS was described. The spectra characteristics, the effect factors, optimum conditions of the reaction, the influence of foreign substances and the reaction mechanism have been investigated. On the optimum reaction conditions, the intensity ofΔ/is directly proportional to the concentration of erythrosine in a certain concentration range and its detection limit is 7.4 ng/mL. It is also shown that this method has high sensitivity, and it can be applied to the determination of erythrosine in candy and drink with satisfactory results.(2) Cationic surfactants-phloxine-systemsResonance Rayleigh scattering (RRS) spectra for the interaction of phloxine with five cationic surfactants (CS) in the NaAc-HCl buffer solution were studied. The spectral characteristics, the effect factors, optimum conditions of the reaction and the influence of foreign substances have been investigated. It is shown that five cationic surfactants (CS) can bind with phloxine to form the ion-association complexes, resulting in the great enhancement of RRS and new RRS spectra appeared. The maximum RRS peaks are all located at 282 nm and smaller peaks are located at 337 nm, 588 nm, respectively. The intensity ofΔ/is directly proportional to the concentration of phloxine in a certain concentration range. Their detection limits for the different systems, whose order of sensitivity from high to low ranks as Zeph>TPB>CPB>CDBAC>CTAB are in the range of 7.37～43.30 ng/mL. Its procedure is easy and rapid, and a method has been developed for the determination of phloxine with cationic surfactants (CS).3. Determination of nutritional fortification substances iodate and iodide by resonance Rayleigh scattering (RRS) method(1) Determination of iodate using potassium iodide-ethyl violet systemIt is discovered that in phosphoric acid solution, potassium iodate react with potassium iodide to form I3- anion complex. I3- can further react with ethyl violet (EV) to form an ion-association complex, which results in the change of absorption spectrum and the great enhancement of resonance Rayleigh scattering (RRS) . The maximum RRS wavelength is located at 319 nm. The intensity ofΔ/is directly proportional to the concentration of potassium iodate in the range of 2.33×10-3～3.00μg/mL. It is shown that this method has high sensitivity, its detection limit is 0.7 ng/mL. It also has a good selectivity and it can be applied to the determination of potassium iodate in table salt.(2) Determination of iodide using [I2Br-]-xanthene dyes systemsIn the presence of PVA and large excessive Br-, I- is selectively oxidized by Cr(Ⅵ) to form I2, which reacts with Br- to form anion complex of [I2Br]-, [I2Br]- can further react with xanthene dyes such as rhodamine 6G,rhodamine B,acridine red to form an ion-association complex, which results in the change of absorption spectrum and fluorescence spectrum and the great enhancement of resonance Rayleigh scattering (RRS). Spectral characteristics have a little difference among different systems. But the intensity ofΔ/is different, whose order of sensitivity from high to low ranks as rhodamine 6G>rhodamine B≈acridine red. The intensity ofΔ/is proportional to the concentration of iodine. Their detection limits for the different systems are in the range of 1.70 ng/mL～4.02 ng/mL. The effect factors, optimum conditions of the reaction and the influence of foreign substances have been investigated. It is shown that this method has a good selectivity and it can be applied to the determination of potassium iodine in laver, kelp and soya bean.
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