DAN - Apresentações orais em encontros internacionais
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- Antioxidant activity and characterization of antioxidants from Argentina OcaPublication . Rego, Andreia; André, Catarina; Delgado, Inês; Samman, Norma; Castanheira, IsabelOverview: - Objectives - Introduction • Oca • Phenolic compounds - Methods • Sample • Extraction Method • Antioxidant activity • Total Phenolic Content • UPLC-PDA - Results and Discussion • DPPH • TPC • UPLC-PDA - Conclusions
- Contribution of metrology on determination of acrylamide in foodstuffsPublication . André, Catarina; Delgado, Inês; Jesus, Susana; Ramos, Ana; Brandão, Carlos; Félix, Nelson; Castanheira, IsabelThe aim of this study was the determination of acrylamide in food with high consumed in Portugal. Samples were bought randomly from local supermarkets and from Escola Superior de Hotelaria e Turismo do Estoril. Sample preparation involved SPE (Solid Phase Extraction). Two chromatographic methods were developed, UPLC-PDA and UPLC-MS/MS which was more suitable and quantify unequivocally acrylamide. The acrylamide content in bread and pastries samples analyzed were above the indicative values published by EFSA.
- Design of experiments to optimized the determination of TDIs in agglomerated cork stoppersPublication . André, Catarina; Delgado, Inês; Matos, Ana Sofia; Castanheira, IsabelIsocyanates are included into a class with an extreme commercial importance because their use in the manufacture of polyurethanes. Polyurethanes are used in several applications such as adhesives, coatings, foams, thermoplastics resins, printing inks, foundry moulds and rubbers. Agglomerated cork stoppers are currently used for still wines, semi-sparkle and gaseous wines, beer and cider. Methylene diphenyl diisocyanate (MDI) is presently the isocyanate used in the production of polyurethane based adhesive in use due to its lowest toxicity comparing with toluene diisocyanate (TDI) previously employed. However, free monomeric TDI or MDI, depending on the based polyurethane, can migrate from agglomerated cork stoppers to beverages therefore it needs to be under control. The presence of these compounds are usually investigated by HPLC with Fluorescence or UV-Vis detector depending on the derivatising agent. Ultra Performance Liquid Chromatography with Diode Array Detector (UPLC-DAD) method is replacing HPLC. The objective of this study is to determine which method is better to analyze isocyanates from agglomerated cork stoppers, essentially TDI to quantify its monomer. A Design of Experiments (DOE) with three factors, column temperature, flow and solvent, at two levels was done. Eight experiments with three replications and two repetitions were developed. Through an ANOVA the significance of the factors was evaluated and the best level’s factors were selected. As the TDI has two isomers and in this method these two isomers were not always separated an ANOVA with results of resolution between peaks was performed. The Design of Experiments reveals to be a suitable statistical tool to determine the best conditions to quantified free isocyanates from agglomerated cork stoppers to real foodstuff. The best level’s factors to maximize area was column temperature at 30ºC, flow to 0,3 mL/min and solvent 0,1% Ammonium Acetate, to maximize resolution was the same except the solvent that was 0,01% Ammonium Acetate.
- HPLC-ICP-MS & ICP-MS applications in Food Analysis: Portuguese experiencePublication . Coelho, Inês; Gueifão, Sandra; André, Catarina; Castanheira, IsabelOs trabalhos publicados na última década têm demonstrado de forma inequívoca que as formas químicas dos elementos, nos sistemas biológicos, são cruciais para se conhecer a sua toxicidade e biodisponibilidade. Nesta comunicação é feita uma revisão bibliográfica das estratégias analíticas mais adequadas para a identificação das espécies químicas dos contaminantes eventualmente existentes nos alimentos ou nos materiais em contacto com alimentos. As técnicas hifenadas como acoplação de um cromatógrafo líquido de alta resolução a um espectrómetro de massa com plasma indutivo acoplado permitem aliar o poder de separação do primeiro à elevada selectividade e sensibilidade do segundo, tornando-se assim nas técnicas de eleição para a especiação química. È feita depois uma breve apresentação dos trabalhos mais recentes publicados sobre a especiação do Arsénio, Crómio, Vanádio, Selénio, Mercúrio e Estanho. È apresentado o Laboratório de ICP-MS, em funcionamento no INSA, sendo discutidos os trabalhos desenvolvidos no âmbito dos Projectos de Investigação, a decorrer. Serão debatidas as abordagens escolhidas para a extracção das espécies de Arsénio em função da sua reactividade e tipo de amostra e os métodos de controlo de qualidade seleccionados para monitorar a estabilidade das espécies e impedir a interconversão das mais reativas. Por fim serão apresentados os projectos a iniciar em 2012 e as tarefas acometidas ao Laboratório de ICP-MS do INSA.