Percorrer por autor "Melo, Armindo"
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- Acute and chronic toxicity assessment of haloacetic acids using Daphnia magnaPublication . Melo, Armindo; Ferreira, Cláudia; Ferreira, Isabel M.P.L.V.O.; Mansilha, CatarinaHaloacetic acids (HAAs) are undesirable disinfection by-products (DBPs), released into aquatic ecosystems from various anthropogenic and natural sources. The aim of this study was to examine the ecological risk of exposure to three HAAs commonly detected in water, such as monobromoacetic acid (MBA), monochloroacetic acid (MCA), and trichloroacetic acid (TCA), in in vivo acute and chronic toxicity tests using Daphnia magna as a model. Acute tests showed that MBA was the most toxic of these compounds followed by MCA and TCA as evidenced by immobilization. Aquatic organisms in natural conditions might be exposed simultaneously to numerous compounds; thus, binary mixtures of selected HAAs and a ternary mixture of these were tested. Concentration addition (CA) and independent action (IA) models were used for a predictive assessment of mixture toxicity. Data demonstrated that CA appeared to be the most reliable indicator for HAAs binary and ternary mixtures suggestive of an additive behavior. Median effective concentration (EC50) values from the mixed exposure tests were significantly lower than results obtained from single tests for all three HAAs where an increase of toxicity greater than 50%. Multigenerational chronic tests were also performed exposing daphnids to the ternary mixture of HAAs. A markedly decreased sexual maturity and number of offspring and broods per daphnid especially in the second generation were noted.
- Analysis of Pesticides in Tomato Combining QuEChERS and Dispersive Liquid–Liquid Microextraction Followed by High-Performance Liquid ChromatographyPublication . Melo, Armindo; Mansilha, Catarina; Pinho, Olívia; Ferreira, Isabel M.P.L.V.O.A new sample preparation procedure combining QuEChERS and dispersive liquid–liquid microextraction (DLLME) was optimized for the determination at trace levels of 13 pesticides from different chemical families (i.e. 2,4-D, acetamiprid, bentazone, cymoxanil, deltamethrin, dicamba, diuron, foramsulfuron, mesotrione, metalaxyl- M, methomyl, pyraclostrobin and tembotrione) in tomato by high-performance liquid chromatography with diode array detection. Target pesticides from tomato samples were isolated by liquid partitioning with acetonitrile and salts and cleaned up by dispersive solid-phase extraction (d-SPE); the analytes were concentrated in trichloromethane by the DLLME procedure. The disperser solvent from DLLME was used at the same time as carrier of analytes form extraction in QuEChERS method. The main factors affecting sample cleanup by d-SPE in QuEChERS and DLLME yield were optimized by means of an experimental design.Under the optimum conditions, good linearity was obtained, the recoveries of pesticides in tomato samples at spiking levels between 0.01 and 1.00 mg/kg ranged from 86 to 116 % (for foramsulfuron and cymoxanil, respectively). Precision was within 15.0 % (RSD) except at the LQ for tembotrione, which was 17.4 %. Limits of quantification achieved (ranging from 0.0058 to 0.15 mg/kg) were below the maximum residue limits established by the European Union.
- Analysis of total extractable hydrocarbons in environmental water samples. Implementation and validation of a FT-IR methodPublication . Pinho, Carina; Melo, Armindo; Mansilha, Catarina; Gameiro, Paula
- Dispersive Liquid–Liquid Microextraction for the Simultaneous Determination of Parent and Nitrated Polycyclic Aromatic Hydrocarbons in Water SamplesPublication . Borges, Bárbara; Melo, Armindo; Ferreira, Isabel M.P.L.V.O.; Mansilha, CatarinaA new method for simultaneous extraction and quantification of 6 nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) and 16 parent polycyclic aromatic hydrocarbons (PAHs) in water matrices was optimized and validated. The extraction procedure was based on dispersive liquid-liquid microextraction technique, followed by gas chromatography-mass detection. The optimum conditions of extraction (volume of the extraction solvent, dispersive solvents and amount of salt) were selected using central composite design. The best results were found by using 200 μL of acetonitrile as dispersive solvent, 60 μL of chloroform as extraction solvent, and 10% (w/v) NaCl. Excellent linearity was observed in the range of 10–150 ng L−1 with correlation coefficients (r2) ranging between 0.9996 and 0.9999 for nitro-PAHs and in the range of 5–150 ng L−1 with r2 ranging from 0.9998 to 1.000 for PAHs. The limits of detection for the nitro-PAHs studied ranged from 0.82 to 3.37 ng L−1, whereas for PAHs ranged from 0.62 to 3.48 ng L−1. The intra- and inter-day precisions for nitro-PAHs were in the range of 0.45 to 19.54% and 0.43 to 19.62%, respectively, and for PAHs ranged between 0.45 to 17.42% and 0.38 to 18.97%, respectively. The proposed method was successfully applied in analyses of groundwater, sea, rain water and river water, being appropriate for routine analyses.
- Environmental impact of intensive horticulture practices on groundwater content of nitrates, sodium, potassium and pesticidesPublication . Pinto, Edgar; Melo, Armindo; Mansilha, Catarina; Ferreira, Isabel
- 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.
- Modeling of α-acids and xanthohumol extraction in dry-hopped beersPublication . Machado, Júlio C.; Faria, Miguel A.; Melo, Armindo; Martins, Zita E.; Ferreira, Isabel M.P.L.V.O.The practice of dry-hopping has been used by the brewing industry to obtain beers with increased contents of flavor and bitterness compounds. Notwithstanding this, other compounds such as α-acids (AA) and xhanthohumol (XN) are co-extracted influencing the final characteristics of the beer, particularly its beneficial bioactivity. In this context a model for the understanding of AA and XN extraction by dry-hopping is proposed. The varieties Chinook (CHI), East Kent Goldings (EKG) and Tettnanger (TET) were assayed and robust statistical approaches were applied for data interpretation. Concentration of AA in beers post-maturation reached values higher than 20 mg/L using 2.8 g/L of CHI hops and 10 days of maturation. For XN, a similar behavior was verified. The maximum efficiency of AA and XN extraction (transfer rate) were reached at 13.5 days with dose rates of 147 and 13.9 mg/L, respectively.
- Monitoring pesticide residues in greenhouse tomato by combining acetonitrile-based extraction with dispersive liquid–liquid microextraction followed by gas-chromatography–mass spectrometryPublication . Melo, Armindo; C. Cunha, Sara; Mansilha, Catarina; Aguiar, Ana; Pinho, Olívia; Ferreira, Isabel M.P.L.V.O.A multiclass and multiresidue method for pesticide analysis in tomato was validated. Extraction and preconcentration of the pesticide residues from acetonitrile extracts was performed by using dispersive liquid–liquid microextraction (DLLME) technique, followed by gas chromatography–mass detection. DLLME was performed using carbon tetrachloride as extractive solvent and acetonitrile extract as dispersive solvent, in order to increase enrichment factor of the extraction procedure. Validation parameters indicated the suitability of the method for routine analyses of thirty pesticides in a large number of samples. In general, pesticide recoveries ranged between 70% and 110% and repeatability ranged between 1% and 20%. The proposed method was applied to the monitoring of pesticides in tomatoes grown during winter in greenhouses. Among the compounds considered in this work, cyprodinil was found in tomato at concentrations of 0.33 mg/kg, other pesticides like azoxystrobin, fenhexanid, tolyfluanid, k-cyhalothrin and trifloxystrobin were also detected, but, not quantified.
- Nutritional quality of protein concentrates from Moringa Oleifera leaves and in vitro digestibilityPublication . Benhammouche, Tassadit; Melo, Armindo; Martins, Zita; Faria, Miguel A.; Pinho, Susana C.M.; Ferreira, Isabel M.L.P.V.O.; Zaidi, FaridThe nutritional value and digestibility of leaf proteins is still a major issue. Therefore, the goal of this work was to optimize the production of a protein concentrate (PC) from Moringa Oleifera defatted leaves (MODL) by enzymatic extraction using Viscozyme L and evaluate its nutritional quality and digestibility. Protein extraction conditions were screened using a factorial design. Enzyme/Substrate ratio and pH had no significant effect, whereas, the significant variables, temperature (°C), enzyme concentration and incubation time (h) were optimized by central composite design (CCD). PC contained 55.7% of proteins with a balanced amino acid profile when compared with MODL and higher content of essential amino acids (EAAs) (488.6-402.9 mg/g of protein respectively). Improvement on protein digestibility was observed for MODL compared to PC (64.75-99.86% respectively) and higher protein digestibility corrected amino acid score (PDCAAS) (62.10-91.41% respectively). PC meets FAO protein quality expectations.
- Occurence of persistent environmental pollutants in freshwaterPublication . Jordão, Luisa; Mansilha, Catarina; Melo, Armindo; Nogueira, Isabel; Veber, Alexander; Puskar, Ljiljana; Schade, UlrichFreshwater pollution is a huge concern. Occurence of 2 groups of persistent pollutants with similar chemical properties (polycyclic aromatic hydrocarbons and microplastics) in Alqueva’s surface water were evaluated during 2021. Samples were collected, once per season, at 3 spots related to touristic activities. Biofilm presence on plastic and natural materials was monitored and compared.