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EM - IUEM - Técnicas Laboratoriais Forenses

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Browsing EM - IUEM - Técnicas Laboratoriais Forenses by Author "Adusei, Emmanuel"

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  • The use of wavelength-dispersive x-ray fluorescence (WDXRF) spectroscopy and multivariate techniques for the assessment of illegal dyes in spices
    Publication . Adusei, Emmanuel; Gonçalves, Luísa Lima
    Sudan dyes are synthetic azo and diazo compounds that are banned for use in food worldwide including the European Community due to their potential toxicity to humans. The ability of WDXRF spectroscopic technique to predict the levels of adulteration of paprika and sweet pepper suspected to be adulterated with Sudan I-IV, Para Red and Sunset Yellow FCF dyes was investigated in this study. Logistic regression and discriminant analysis classification models were developed to predict the type of adulteration using WDXRF spectral features such as the Compton and Rayleigh scatter intensities and the Compton and Rayleigh ratios. Prediction of the levels of adulteration was assessed by using multiple regression analysis. 83% of the 210 adulterated samples were correctly classified by the logistic regression with 90% sensitivity, 75%specificity with a prediction power of 92% into respective adulteration groups. 86% and 90% correct prediction were obtained for discriminant analysis models with 94% sensitivity and 74% specificity. Three multiple regression models were performed for each data set. Models based on the Compton and Rayleigh ratios, Compton and Rayleigh scatter intensities as well as a full model based on both ratios and scatter intensities were developed and compared with each other. The full model revealed to be the best model to predict the levels of adulteration with an adjusted R2 between 95.1 to 99.0% with the errors of estimate between 1.6 to 3.7%.
    2014-07Master thesis Open access Show more