Browsing by Author "Viegas, Olga"
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- Fast and Reliable Extraction of Polycyclic Aromatic Hydrocarbons from Grilled and Smoked Muscle FoodsPublication . Silva, Marta; Viegas, Olga; Melo, Armindo; Finteiro, Daniela; Pinho, Olívia; Ferreira, Isabel M. P. L. V. O.A fast and simple method for analysis of 14 PAHs in grilled and smoked muscle foods using acetonitrile based-extraction was validated. The optimum amounts of magnesium sulfate and sodium chloride that promoted phase separation of acetonitrile extract containing PAHs from water phase were selected by Central Composite Design. Matrix-matched calibration curves were constructed by adding different concentrations of PAHs and then subjected to extraction followed by HPLC with fluorescent detection. An excellent linearity for all compounds applying weighed least squares linear regression procedure was achieved. LODs and LOQs were lower than 0.12 and 0.39 ng g−1 respectively. Validation was done according to International Conference on Harmonization recommendations for 14 PAHs. The criteria for 4 EU marker PAHs (benz[a]anthracene, chrysene, benzo[b]fluoranthene and benzo[a]pyrene) established by European Comission Regulation No. 836/2011 was also accomplished. Repeatability and reproducibility were lower than 8 and 13.3%, and the most of recoveries fall in the range of 80–110% in different grilled and smoked muscle foods. The proposed method is a robust tool for determination of PAHs in grilled and smoked muscle foods, being easy to perform in short time.
- Simultaneous determination of melatonin and trans-resveratrol in wine by dispersive liquid–liquid microextraction followed by HPLC-FLDPublication . Viegas, Olga; Esteves, Cristina; Rocha, Janete; Melo, Armindo; Ferreira, Isabel M.P.L.V.O.The discovery of melatonin (Mel) in wines triggered a new interest in the paradigm of health benefits and wine consumption, usually ascribed to trans-resveratrol (trans-RSV). In this context, a dispersive liquid-liquid microextraction for the analysis of Mel and trans-RSV in wines by LC-FLD was developed. A 26-1 factorial design was used to identify the significant variables (p < 0.05) and Central Composite Design was used to achieve the optimal conditions: 300 µL of chloroform (extracting solvent), 1500 µL of acetonitrile (disperser solvent) and 1500 mg of NaCl (ionic strength). Excellent linearity (R2 > 0.9999), repeatability (<3.55%), and accuracy (<7.18%) were obtained using a blank matrix and recoveries (>91.9%) using wines. The method was successfully applied to the analyses of Mel (0.63-7.44 ng mL-1) and trans-RSV (169-2616 ng mL-1) in different wine varieties. Comparison with literature point the overall advantages of the new method.