| Recently, the new analytical techniques of resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering (FDS) have been given much attention because of their high sensitivity, simplicity and rapidness, and have been studied more and more. At present, they have been applied to the study and determination of macromolecules such as nucleic acids, proteins, polysaccharides, surfactants, inorganic ions, Pharmaceuticals, lysozyme, and triphenylmethane dyes. In particular, with the rapid development of nanotechnology, great attention has been focused on the use of nanoparticles and quantum dots (QDs) as the RRS probes, such as Au nanoparticles, Ag nanoparticles, core-shell of Au-Ag nanoparticles and QDs. In addition, it has been applied to the determination ofβ-cyclodextrin inclusion constant and the critical micelle concentration of surfactant. In this paper, the RRS, SOS, and FDS spectra and their application of the interaction between food color erythrosine (Ery) and Fe(phen)32+ in the absence and presence of organic solvent, and of the interaction between Ery and cationic surfactant have been studied. The spectra characteristics, influencing factors, interaction mechanism and their analytical applications have been investigated. Meanwhile, the establishment of the RRS method for the determination of food colour Ery was a significant innovation of the application RRS technique. The main contents are as follows:1. Resonance Rayleigh scattering, second-order scattering and frequency doubling scattering spectra for studying the interaction of erythrosine with Fe(phen)32+ and its analytical applicationIn a weak alkaline Britton-Robinson buffer medium, erythrosine (Ery) can react with Fe(phen)32+to form 1:1 ion-association complex, which will cause not only the changes of the absorption spectra, but also the remarkable enhancement of resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering (FDS) spectra, and the appearance of new spectra of RRS, SOS and FDS. The maximum RRS, SOS and FDS wavelengths (λex/λem) of the ion-association complex are located at 358/358 nm,290/580 nm and 780/390 nm, respectively. The increments of scattering intensities (ΔI) are directly proportional to the concentration of Ery in a certain range. The detection limits for Ery are 0.028μg mL-1 for RRS method,0.068 ng mL-1 for SOS method andμg mL-1 for FDS method, respectively. Among them, the RRS method has the highest sensitivity. Based on the above researches, a new highly sensitive and simple method for the determination of Ery in drinks has been developed. In this work, the spectral characteristics of absorption, RRS, SOS and FDS spectra, the optimum conditions of the reaction and influencing factors for the RRS, SOS and FDS intensities were investigated. In addition, the reaction mechanism was discussed.2. Study of the ethanol sensitizing effect on the interaction of erythrosine and Fe(phen)32+ by resonance Rayleigh scattering, second-order scattering and frequency doubling scattering spectra and its analytical applicationIn a weak acidic Britton-Robinson buffer medium, erythrosine can react with Fe(phen)32+ to form 2:1 ion-association complex in the presence of ethanol, which will cause not only the change of the absorption spectrum, but also the remarkable enhancement of RRS, SOS, and FDS spectra, and the appearance of new spectra of RRS, SOS, and FDS. The maximum wavelengths (λex/λem) of the ion-association complex are located at 350 nm/350 nm for RRS,280 nm/560 nm for SOS, and 780 nm/390 nm for FDS, respectively. The increments of scattering intensities (ΔI) are directly proportional to the concentration of Ery in a certain range. The detection limits for Ery are 5.6 ng mL-1 for RRS method,13 ng mL-1 for SOS method, and 17 ng mL-1 for FDS method, respectively. In this work, the spectral characteristics of absorption, RRS, SOS, and FDS spectra, the optimum conditions of the reaction and influencing factors were investigated. In addition, the reaction mechanism was discussed. Based on the above researches, a new highly sensitive and simple method for the determination of Ery in drink samples has been developed.3. Determination of erythrosine with organic solvents in food by resonance Rayleigh scattering, second-order scattering and frequency doubling scattering methodsA novel and sensitive assay has been developed to investigating the interaction of Ery with five organic solvents such as ethanol, methanol, acetone, acetonitrile, and DMSO via using RRS, SOS, andFDS techniques in 0.05-0.15 mol L-1 HCl medium. The results show that the reaction conditions and RRS spectra characteristics of the four organic solvents are similar, except for acetone, but their sensitivities are distinctly different. Among them, the sensitivity of ethanol is the highest, while that of acetone or acetonitrile is the lowest. Take Ery-ethanol system as example, the maximum wavelengths (λex/λem) of the polymer are located at 338nm/338nm for RRS,275 nm/550 nm for SOS, and 660 nm/330 nm for FDS, respectively. The increments of scattering intensities (ΔI) are directly proportional to the concentration of Ery in a certain range. The detection limit for Ery of the former is 8.1 ng mL-1, and that of the later is 15 ng mL-1 for RRS method,21 ng mL-1 for SOS method, and 33 ng mL-1 for FDS method, respectively. The method was applied to the determination of Ery in various water-soluble foods with satisfactory results. Meanwhile, the spectral characteristics of absorption, RRS, SOS, and FDS spectra, the optimum conditions of the reaction and influencing factors were investigated. In addition, the reaction mechanism was discussed.4. A highly sensitive resonance Rayleigh scattering spectrum assay for erythrosine with cationic surfactants and its analytical applicationA sensitive assay has been developed to investigating the interaction of Ery with five cationic surfactants such as cetyldimethyl benzylammonium chloride (CDBAC), zephiramine (Zeph), cetylpyridinium bromide (CPB), cetylpyridinium chloride (CPC) and cetyl trimethylammonium bromide (CTAB) in a weak acidic Britton-Robinson buffer medium via using resonance Rayleigh scattering technique. The results show that the reaction conditions and RRS spectra characteristics for the five cationic surfactants are similar, but their sensitivities are distinctly different. Among them, the sensitivity of CDBAC is the highest, while that of CTAB is the lowest. The detection limit for Ery of the former is 8.0 ng mL-1, and that of the later is 15 ng mL-1. In this work, the reaction conditions and the influencing factors have been investigated, and the effects of coexisiting sustances also have been examined indicating a good selectivity of the method. It can be applied to the determination of Ery in food samples with satisfactory results. In the meantime, it is also found that the RRS intensity is concerned with the structure and molecular weight of the cationic surfactant.
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