Percorrer por autor "Ferreira, Isabel M.P.L.V.O."
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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.
- 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.
- 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.
- Occurrence of Trihalomethanes in Chlorinated Waters from Different Sources Used for Urban SupplyPublication . Melo, Armindo; Mansilha, Catarina; Margarida, Teixeira; Ferreira, Isabel M.P.L.V.O.Trihalomethanes (THMs) are the most common disinfection by-products formed by the reaction of chlorine and/or bromide with organic matter. Total THMs in chlorinated treated water are defined as the sum of the concentrations of chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform (TBM). The monitoring of trihalomethanes in distribution tap water collected in from five regions of Portugal, from North to South, in a total of 33 samples, during spring to summer season, is described. Solid phase microextraction coupled to gas chromatography and electron capture detector methodology was applied to determine whether THMs concentrations in urban water supply systems are is in agreement with European Regulations. It was found a great discrepancy in total THMs concentration values, with concentrations varying from 1.8-97.7 μg/L, although the results were below the European parametric value of 100 μg/L. Regarding the Environmental Protection Agency regulations, however, only 97% of samples fulfilled the established criterion of 80 μg/L. and investigate if the individual compounds trihalomethanes content in was also investigated in order to determine if there is observed distribution tap water follows a common or a different THMs pattern in close geographical areas. In the geographical areas under study, mean values of concentrations measured revealed two different clusters: one including the three groups from the North geographical areas, with samples revealing a similar pattern (TCM>BDCM>DBCM>TBM), and another including the two groups from South with a different THMs pattern (DBCM>BDCM>TCM>TBM). A great degree of variation in the concentrations of THMs in tap water was observed, although the results the total THMs concentrations were below the European parametric value (100 μg/L). Mean results of samples grouped by five geographical areas revealed a similar pattern in samples collected from North and Centre TCM>BDCM>DBCM>TBM, whereas samples from South presented a different pattern, DBCM>BDCM>TCM>TBM. The origin of raw water (surface or groundwater) seems to influence this different pattern formation of brominated compounds.
- 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.
- Simultaneous Extraction and Determination of Preservatives and Antioxidants in Juice Samples by an Optimized Microextraction Method Using Central Composite Design and Validated with Accuracy ProfilePublication . Tighrine, Abderrahmane; Pinto, Edgar; Melo, Armindo; Ferreira, Isabel M.P.L.V.O.; Mamou, Marzouk; Amir, YoucefBackground: Food additives are widely used in industries. Overall, these additives have a beneficial role, but if their concentration exceeds certain limits, they may have an adverse effect on human health. Objective: This study outlines the determination of benzoic acid (BA), sorbic acid (SA), butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT) in juices using dispersive liquid-liquid microextraction and HPLC-diode-array detection. Methods: Different parameters that significantly affect the extraction efficiency were optimized. The disperser and extraction solvents were acetone and chloroform, respectively. The other parameters were selected and optimized using two-level (2k) factorial and central composite designs, respectively. A full method validation using an accuracy profile for the total measurement error was carried out. Results: The optimized conditions were 625 μL acetone, 350 μL chloroform, 0.85 g NaCl, and pH 2. The validated method demonstrated good linearity with R² ≥ 0.99 and good precision with the RSD of repeatability and intermediate precision at 1.97-10.7% and 2.31-11.9%, respectively. The relative recoveries were 96.2-105.4%, and the LODs were around 0.03 μg/mL for all compounds. The analysis of 41 samples revealed that BA and SA were quantified in 25 and 20 samples, respectively. BHA and BHT were not detected. Conclusions: The proposed methodology is an appropriate tool to determine important food additives in juices to ensure their compliance with the food additives legislation. Highlights: The work has demonstrated that the method can be successfully used in the simultaneous determination of four food additives in fruit juices.