| Food, medicine and environmental water safety issues are closely connected with human health, life security and social harmony, which is an event in the existence and development of human society. Thus, taking efforts to build fine and safe social environment for food, medicine and water has drawn considerable attention from the public and the government. Despite all this, in recent years, new issues of environment pollution, food and drug safety are constantly emerging. Some market traders add large amount of illegal additive and industrial raw materials to food, and even manufacture fake products. Moreover, some enterprises and individuals discharge industrial waste, sewage, chemical fertilizers, and pesticides into the environment directly, which poses a potential risk to human health. Consequently, the development of simple, sensitive, efficient and scientific approaches for monitoring hazardous substances in food, medicine and environmental samples have become very important to public health. In this paper, some hazardous substances such as 6-benzyladenine, perfluorooctane sulfonate and antibiotic medicine ceftriaxone sodium were selected as the research topic. The interacions of them with Pd(Ⅱ), crystal violet and L-tryptophan were studied. The optimal conditions, the mechanisms of the interactions, the spectral features of absorption, resonance Rayleigh scattering and fluorescence were also investigated. Accordingly, novel methods for assay of 6-benzyladenine, perfluorooctane sulfonate and ceftriaxone had been established. Moreover, they have been applied to practical samples successfully. The main work of this thesis is as follows:1. Study on 6-Benzyladenine and Pd(Ⅱ) by Resonance Rayleigh scattering, Second Order Scattering and Frequency Doubling Scattering Spectra and Its Analytical ApplicationIn this work, resonance Rayleigh scattering (RRS), second order scattering (SOS) and frequency double scattering (FDS) methods had been developed for sensitive determination of trace 6-benzyladenine (BA) in bean sprout samples. In pH 1.6 HCl-NaAc medium, Pd(II) reacted with BA to form a 1:1 chelate complex, and then the complex further self-aggregated into nanoparticles [Pd(Ⅱ)-BA]n. This resulted in remarkable enhancement of resonance Rayleigh scattering, second order scattering and frequency double scattering spectra. The maximum wavelengths were located at 312 nm (RRS),632 nm(SOS) and 323nm (FDS), respectively. The increments of scattering intensities ΔI were directly proportional to the concentration of BA in certain ranges. The detection limits were 7.0 nmol L-1 (0.79μg kg-1, RRS),10.3 nmol L-1 (1.16μg kg-1, SOS) and 39.4 nmol L-1 (4.44μg kg-1, FDS). In addition, the optimum conditions of the reaction, and the effects of coexisting substances were investigated. The results showed that these methods exhibited a high selectivity. The reaction mechanism and the reasons for the enhancement of scattering were also discussed. The proposed method had been successfully applied to determine trace amount of BA in bean sprout samples with the recoveries of 97.0～103.0%.2. Triple-wavelength overlapping resonance Rayleigh scattering method for rapid assay of perfluorooctane sulfonate in surface and drinking waterIn the present study, a novel triple-wavelength overlapping resonance Rayleigh scattering (TWO-RRS) method had been well-established to detect perfluorooctane sulfonate (PFOS). In Britton-Robinson (BR) medium, we found that crystal violet (CV) could react with PFOS to form 1:1 ion-association complex by electrostatic attraction and hydrophobic effect over a wide pH range (5.0-11.0) in less than 60s. The complexes would further self-aggregated into nanoparticles [CV-PFOS]n. Based on this phenomenon, not only the absorption and Raman spectra were changed, but also RRS intensities were significantly enhanced. And three new RRS peaks located at 327,492 and 654 nm were clearly observed, respectively. At the same time, it was found that both the enhanced single-wavelength resonance Rayleigh scattering (SW-RRS) and TWO-RRS intensities against the concentration of PFOS showed excellent correlation. The detection limits for the three single peaks were 27.4 nmol L-1 (13.7μg L-1,327 nm) 27.5 nmol L-1 (13.8μgL-1,492 nm), and 31.4 nmol L-1 (15.7μg L-1,654 nm), and for TWO-RRS method was 5.9 nmol L-1 (3.0μg L-1). Moreover, it could be applied to determine PFOS water samples successfully.3. A "Turn-On" Fluorescent Strategie for Rapid and Sensitive Ceftriaxone Detection Based on L-tryptophan-Pd(Ⅱ) Complex Fluorophore in Human UrineBased on L-tryptophan-Pd(II) system, a sensitive and selective fluorimetric assay for the quantification of ceftriaxone (CTRX) had been developed. The experimental results showed that in pH 4.0 Britton-Robinson (BR) buffer medium, the fluorescence of L-tryptophan (L-Trp) (λex/λem=276 nm/352 nm) could be efficiently quenched by Pd(Ⅱ). When CTRX was added to the mixed solution of the L-tryptophan and Pd(Ⅱ), the fluorescence of L-Trp recovered. The reaction mechanism and the reasons for the fluorescence recovery were also discussed. Pd(Ⅱ) reacted with L-Trp to form a 1:1 chelate complex, and then, after CTRX was added in L-Try-Pd(Ⅱ) system, the ligand exchange reaction occurred between L-Trp and CTRX, which resulted in the fluorescence recovery. Under the optimized experimental conditions, the recovered fluorescence intensities at 352 nm linearly correlated with the concentration of CTRX over the range of 6.0×10-8～2.4×10-6 mol L-1 (0.040～1.59μg mL-1) with the correlation coefficients (R) is 0.9997. The detection limit was 1.8×10-8 mol L-1 (11.9 ng mL-1). Furthermore, the assay had been applied applied to determine trace amount of CTRX human urine samples with satisfactory results. |
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