DAN - Dissertações de mestrado
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Browsing DAN - Dissertações de mestrado by Author "Carvalho, Cláudia"
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- Determinação analítica de nitratos e/ou nitritos em amostras do estudo de dieta total (TDS) por cromatografia líquida de alta resolução (HPLC): contribuição para a avaliação da exposição da população a nitratos/nitritosPublication . Carvalho, Cláudia; Serra, Maria Celeste; Vasco, Elsa ReisThe main purpose of this work was the optimization and validation of an ion exchange HPLC method for the determination of nitrate and nitrite contents in meat food samples, based on the European Standard EN 12014-4, for application in the analysis of these products. The analytical determination was run on an HPLC equipment with UV-Vis DAD detector, using mobile phase based on lithium borate gluconate buffer and acetonitrile. The samples were extracted with hot water, while clarification was achieved with acetonitrile. Detection was performed at 205 nm. Through the optimization tests, the laboratory was able to confirm that the parameters indicated in the European Standard were adequate. The only change was in the preparation of the standards, which were prepared in mobile phase instead of water that allow a better visualization and integration of the peaks of interest. The method validation procedure consisted in the evaluation of parameters such as selectivity/specificity, range of work, linearity, sensitivity, repeatability and linearity of the injector, detection limits (3.3 mg nitrate/kg sample and 1.7 mg nitrite/kg sample) and quantification (10 mg nitrate/kg sample and 5 mg nitrite/kg sample), precision (coefficients of variation below 10%) and accuracy. From the analysis of the samples it was possible to verify that only two samples were above the limits of potassium nitrate allowed, with contents of 648 and 1 190 mg/kg sample, in the samples of pork pate and salami, respectively. It was possible to compare different batches of the same sample through an ANOVA test with a significance level of 5% and to conclude that the batches differed significantly, probably due to interconversion of the analytes during storage. Finally, the exposure of the population to the analyzed analytes was evaluated and it was verified that the consumption of meat products does not contribute for the exposure of the population to nitrates and nitrites, since were found values below 0.01 mg/body weight/day.