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Percorrer por autor "Nunes, Ana"

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  • Determination of iron(III) in water samples by microsequential injection solid phase spectrometry using an hexadentate 3-hydroxy-4-pyridinone chelator as reagent
    Publication . Miranda, Joana L. A.; Mesquita, Raquel B. R.; Nunes, Ana; Rangel, Maria; Rangel, António O. S. S.
    In this work, the hexadentate 3,4–hydroxypyridinone ligand was used as reagent for the spectrophotometric quantification of iron(III) in fresh and sea waters, using a micro sequential injection lab-on-valve (μSI-LOV) system in a solid phase spectrometry (SPS) mode. To implement SPS, thus eliminating the sample matrix, a packed column in the flow cell was used; the chosen sorbent was Nitrilotriacetic Acid Superflow resin (NTA). The possibility of performing an analytical curve resorting to just one standard was also demonstrated. The consumption of the hexadentante ligand was about 30 μg per determination and the effluent production lower than 2.5 mL. The dynamic concentration range was 0.45–9.0 μmol L−1, with a limit of detection of 0.13 μmol L−1 and limit of quantification 0.43 μmol L−1. The proposed μSI-LOV-SPS methodology was successfully applied to river, ground, estuarine, tap, and sea waters.
    2019Artigo científico Acesso restrito Ver mais
  • Population wide testing pooling strategy for SARS-CoV-2 detection using saliva
    Publication . Esteves, Eduardo; Mendes, Ana Karina; Barros, Marlene; Figueiredo, Cátia; Andrade, Joana; Capelo, Joana; Novais, António; Rebelo, Carla; Soares, Rita; Nunes, Ana; Ferreira, André; Lemos, Joana; Duarte, Ana Sofia; Silva, Raquel M.; Bernardino, Liliana Inácio; Correia, Maria José; Esteves, Ana Cristina; Rosa, Nuno
    SARS-CoV-2 pandemic has forced frequent testing of populations. It is necessary to identify the most cost-effective strategies for the detection of COVID-19 outbreaks. Nasopharyngeal samples have been used for SARS-CoV-2 detection but require a healthcare professional to collect the sample and cause discomfort and pain to the individual. Saliva has been suggested as an appropriate fluid for the diagnosis of COVID-19. We have investigated the possibility of using pools of saliva samples to detect SARS-CoV-2 in symptomatic and asymptomatic patients. Two hundred and seventy-nine saliva samples were analyzed through RT-PCR of Envelope, Nucleocapsid and Open Reading Frame 1ab genes. Reproducibility assays showed an almost perfect agreement as well as high sensitivity (96.6%), specificity (96.8%), positive predicted value (96.6%), and negative predicted value (96.8%). The average Cycle Threshold of the genes detected was 29.7. No significant differences (p > 0.05) were detected when comparing the cycle threshold average of two consecutive reactions on the same positive saliva samples. Saliva samples have a higher median viral load (32.6) than in nasopharyngeal samples (28.9), although no significant differences were detected (p > 0.05). Saliva-pool samples allowed effective SARS-CoV-2 screening, with a higher sensibility (96.9%) on 10-sample pools than in 20-sample pools (87.5%). Regardless of pools size specificity was high (99.9%) and an almost perfect agreement was observed. Our strategy was successfully applied in population wide testing of more than 2000 individuals, showing that it is possible to use pooled saliva as diagnostic fluid for SARS-CoV-2 infection.
    2022-01-28Artigo científico Acesso aberto Ver mais
  • 2012Capítulo de livro Acesso aberto Ver mais