Determination Of Contaminants In Environment And Foodstuffs Using Media Gradual Change-Visible Spectra Coupled With Second Order Calibration Algorithms

In the introductory part of this paper, the domestic and foreign situation in environmental monitoring and food safety was outlined. Then the research developments in the methodology of establishing second order data and in the chemometric algorithms for treating with the data were reviewed emphatically. Meanwhile, the significance for the analysis of 2,4-dinitrophenol, Sudan I, malachite green and crystal violet was stated, and the research development in the analysis of these contaminants was also reviewed. In addition, the new methods proposed by this work for the determination of these contaminants using media gradual change-visible spectra coupled with second order calibration algorithms were also summarized.In Chapter 1, the method for establishing pH changed gradually spectra second order data was introduced, and a new method for the determination of 2,4-dinitrophenol in mixtures using the second order data coupled with rank annihilation factor analysis has been developed. In the method described here, the pH of the whole solution containing the analyte changed gradually by adding sodium hydroxide solution into Britton-Robinson buffer solution. In this process, the absorption sepctra of the solution at different pH were recorded and the acidity-absorbance spectra bilinear matrix was obtained. Then the concentration of 2,4-dinitrophenol in the mixtures could be obtained by rank annihilation factor analysis. The method has been used to determine 2,4-dinitrophenol in environmental mixture samples, and the results are satisfactory with the recoveries of 95.8% ~ 104.7%.In Chapter 2, the method for establishing solvent components gradual change - visible absorption spectra matrix was introduced, and a new method for the determination of Sudan I in gray systems using the spectra matrix coupled with second order calibration algorithms has been developed. The second order calibration algorithms were based on the popular parallel factor analysis (PARAFAC) and rank annihilation factor analysis (RAFA) respectively. In the method described here, the components of the solvent were changed gradually by adding ethanol into cyclohexane, the absorption spectra of Sudan I and chilli samples in a series of cyclohexane-ethanol mixed solvents with various ethanol volume fractions were recorded, and then the second order data were obtained from the solvent components gradual change - visible absorption spectra. Thus, the concentration of Sudan I in a gray system could be determined from the spectra matrices using second order calibration algorithms. The method has been used to determine Sudan I in chilli powder with satisfactory results.In Chapter 3, the method for establishing solvent components gradual change - visible absorption spectra second order data in the presence of thiocyanate was introduced, and a new method for the simultaneous determination of malachite green (MG) and crystal violet (CV) in grey systems using the second order data coupled with second order calibration algorithms has been developed. The second order calibration algorithms were based on the residual bilinearization (RBL). In the method described here, firstly, MG and CV were associated with thiocyanate. The components of the solvent were changed gradually by adding ethanol into water, the absorption spectra of calibration set and samples in a series of water-ethanol mixed solvents with various ethanol volume fractions were recorded, and then the second order data were obtained from the solvent components gradual change - visible absorption spectra. Thus, the concentration of MG and CV in a gray system could be determined from the spectra matrices using RBL.The method has been successfully used to determine simultaneously MG and CV in fish samples with satisfactory results.