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- Chlormequat selective electrodes: construction, evaluation and application at FIA systemsPublication . Ferreira Sales, Maria Goreti; Lino, Nuno F. M. C.; PaĆga, PaulaA flow injection analysis (FIA) system having a chlormequat selective electrode is proposed. Several electrodes with poly(vinyl chloride) based membranes were constructed for this purpose. Comparative characterization suggestedthe use of membrane with chlormequat tetraphenylborate and dibutylphthalate. On a single-line FIA set-up, operating with 1x10-2 mol L-1 ionic strength and 6.3 pH, calibration curves presented slopes of 53.6Ā±0.4mV decade-1 within 5.0x10-6 and1.0x10-3 mol L-1, andsquaredcorrelation coefficients >0.9953. The detection limit was 2.2x10-6 mol L-1 and the repeatability equal to Ā±0.68mV (0.7%). A dual-channel FIA manifold was therefore constructed, enabling automatic attainment of previous ionic strength andpH conditions and thus eliminating sample preparation steps. Slopes of 45.5Ā±0.2mV decade -1 along a concentration range of 8.0x10-6 to 1.0x10-3 mol L-1 with a repeatability Ā±0.4mV (0.69%) were obtained. Analyses of real samples were performed, and recovery gave results ranging from 96.6 to 101.1%.
- Determination of carbamate and urea pesticide residues in fresh vegetables using microwave-assisted extraction and liquid chromatographyPublication . PaĆga, Paula; Morais, Simone; Correia, Manuela; Delerue-Matos, Cristina; Alves, ArmindaAn analytical multiresidue method for the simultaneous determination of seven pesticides in fresh vegetable samples, namely, courgette (Cucurbita pepo), cucumber (Cucumis sativus), lettuce (Lactuca sativa, Romaine and Iceberg varieties) and peppers (Capsicum sp.) is described. The procedure, based on microwave-assisted extraction (MAE) and analysis by liquid chromatographyā photodiode array (LCāPDA) detection was applied to four carbamates (carbofuran, carbaryl, chlorpropham and EPTC) and three urea pesticides (monolinuron, metobromuron and linuron). Extraction solvent and the addition of anhydrous sodium sulphate to fresh vegetable homogenate before MAE were the parameters optimised for each commodity. Recovery studies were performed using spiked samples in the range 250ā403 Āµgkg- 1 in each pesticide. The pesticide residues were extracted using 20mL acetonitrile at 60 ĀŗC, for 10 min. Acceptable recoveries and RSDs were attained (overall average recovery of 77.2% and RSDs are lower than 11%). Detection limits ranged between 5.8 Āµgkg- 1 for carbaryl to 12.3 Āµgkg- 1 for carbofuran. The analytical protocol was applied for quality control of 41 fresh vegetable samples bought in Oporto Metropolitan Area (North Portugal). None of the samples contained any detectable amounts of the studied compounds.
- Presence of pharmaceuticals in the Lis river (Portugal): Sources, fate and seasonal variationPublication . PaĆga, Paula; Santos, LĆŗcia H.M.L.M.; Ramos, Sandra; Jorge, Sandra; Silva, Jaime Gabriel; Delerue-Matos, CristinaThe occurrence of 33 pharmaceuticals and metaboliteswas evaluated along the Lis river and in the influents and effluents of twowastewater treatment plants (WWTPs) located along the river. Results indicate that pharmaceuticals, such as ibuprofen, ketoprofen, carbamazepine and fluoxetine, and the metabolite salicylic acid are widespread along the Lis river, showing 100% of detection frequency, at levels up to 1.3 Ī¼g Lā1. The number of molecules detected increased along the river, with 11 molecules in the source, 15 upstreamWWTP 1, 16 downstreamWWTP 1 and upstreamWWTP 2 and 19 downstream WWTP 2. The highest concentrations were often found downstream near the river mouth. Different possible sources of contamination of the Lis river were identified, namelyWWTP effluents, untreated wastewaters and livestock production. Nevertheless, the discharge of WWTP effluents appeared to be the most pronounced, given that, in general, it was noticed an increase in the concentration of pharmaceuticals downstream of the WWTPs. WWTP effluents contributed with a total mass load of pharmaceuticals into the Lis river between 470 and 2317 mg/d/1000 inhabitants. Non-steroidal anti-inflammatory drugs/analgesics were the therapeutic groupwith a high contribution to the total mass load of pharmaceuticals entering the Lis river, followed by psychiatric drugs and antibiotics. No seasonal variation was observed for the detected concentrations of pharmaceuticals. At the levels detected in the Lis river, sulfamethoxazole, clarithromycin, azithromycin and ibuprofen showed to have potential risk for aquatic organisms. These findings show that further studies embracing different environmental compartments (water, sediment and biota) are needed, in order to evaluate the partition/distribution of pharmaceuticals, their metabolites and transformation products in the environment aswell as to predict their possible impact to non-target organisms and, in a last instance, to human health.
- Analysis of PCBs in soils and sediments by microwave-assisted extraction, headspace-SPME and high resolution gas chromatography with ion-trap tandem mass spectrometryPublication . Herbert, Paulo; Morais, Simone; PaĆga, Paula; Alves, Arminda; Santos, LĆŗciaA procedure for the determination of seven indicator PCBs in soils and sediments using microwave-assisted extraction (MAE) and headspace solid-phase microextraction (HS-SPME) prior to GC-MS/MS is described. Optimization of the HS-SPME was carried out for the most important parameters such as extraction time, sample volume and temperature. The adopted methodology has reduced consumption of organic solvents and analysis runtime. Under the optimized conditions, the method detection limit ranged from 0.6 to 1 ng/g when 5 g of sample was extracted, the precision on real samples ranged from 4 to 21% and the recovery from 69 to 104%. The proposed method, which included the analysis of a certified reference material in its validation procedure, can be extended to several other PCBs and used in the monitoring of soil or sediments for the presence of PCBs.
- Determination of ametryn in soils via microwave-assisted solvent extraction coupled to anodic stripping voltammetry with a gold ultramicroelectrodePublication . Tavares, Oriza; Morais, Simone; PaĆga, Paula; Delerue-Matos, CristinaAn extraction-anodic adsorptive stripping voltammetric procedure using microwave-assisted solvent extraction and a gold ultramicroelectrode was developed for determining the pesticide ametryn in soil samples. The method is based on the use of acetonitrile as extraction solvent and on controlled adsorptive accumulation of the herbicide at the potential of 0.50 V (vs. Ag/AgCl) in the presence of Britton-Robinson buffer (pH 3.3). Soil sample extracts were analysed directly after drying and redissolution with the supporting electrolyte but without other pre-treatment. The limit of detection obtained for a 10 s collection time was 0.021 Āµg g-1. Recovery experiments for the global procedure, at the 0.500 Āµg g-1 level, gave satisfactory mean and standard deviation results which were comparable to those obtained by HPLC with UV detection.
- A multiresidue method for the analysis of carbamate and urea pesticides from soils by microwave-assisted extraction and liquid chromatography with photodiode array detectionPublication . PaĆga, Paula; Morais, Simone; Correia, Manuela; Alves, Arminda; Delerue-Matos, CristinaA multiresidue approach using microwave-assisted extraction and liquid chromatography with photodiode array detection was investigated for the determination of butylate, carbaryl, carbofuran, chlorpropham, ethiofencarb, linuron,metobromuron, and monolinuron in soils. The critical parameters of the developed methodology were studied. Method validation was performed by analyzing freshly and aged spiked soil samples. The recoveries and relative standard deviations reached using the optimized conditions were between 77.0 Ā± 0.46% and 120 Ā± 2.9% except for ethiofencarb (46.4 Ā± 4.4% to 105 Ā± 1.6%) and butylate (22.1 Ā± 7.6% to 49.2 Ā± 11%). Soil samples from five locations of Portugal were analysed.
- Determination of ochratoxin A in bread: evaluation of microwave-assisted extraction using an orthogonal composite design coupled with response surface methodologyPublication . PaĆga, Paula; Morais, Simone; Oliva-Teles, Maria Teresa; Correia, Manuela; Delerue-Matos, Cristina; Sousa, Ana M. M.; GonƧalves, Maria Pilar; Duarte, S. C.; Pena, Angelina; Lino, C. M.An analytical method using microwave-assisted extraction (MAE) and liquid chromatography (LC) with fluorescence detection (FD) for the determination of ochratoxin A (OTA) in bread samples is described. A 24 orthogonal composite design coupled with response surface methodology was used to study the influence of MAE parameters (extraction time, temperature, solvent volume, and stirring speed) in order to maximize OTA recovery. The optimized MAE conditions were the following: 25 mL of acetonitrile, 10 min of extraction, at 80 Ā°C, and maximum stirring speed. Validation of the overall methodology was performed by spiking assays at five levels (0.1ā3.00 ng/g). The quantification limit was 0.005 ng/g. The established method was then applied to 64 bread samples (wheat, maize, and wheat/maize bread) collected in Oporto region (Northern Portugal). OTAwas detected in 84 % of the samples with a maximum value of 2.87 ng/g below the European maximum limit established for OTA in cereal products of 3 ng/g.
- Genotoxicity of gold nanoparticles in the gilthead seabream (Sparus aurata) after single exposure and combined with the pharmaceutical gemfibrozilPublication . Barreto, A.; Luis, L.G.; Pinto, E.; Almeida, A.; PaĆga, Paula; H.M.L.M. Santos, LĆŗcia; Delerue-Matos, Cristina; Trindade, T.; Soares, A.M.V.M.; Hylland, K.; Loureiro, S.; Oliveira, M.Due to their diverse applications, gold nanoparticles (AuNPs) are expected to increase of in the environment, although few studies are available on their mode of action in aquatic organisms. The genotoxicity of AuNPs, alone or combined with the human pharmaceutical gemfibrozil (GEM), an environmental contaminant frequently detected in aquatic systems, including in marine ecosystems, was examined using gilthead seabream erythrocytes as a model system. Fish were exposed for 96āÆh to 4, 80 and 1600āÆĪ¼gāÆL-1 of 40āÆnm AuNPs with two coatings - citrate or polyvinylpyrrolidone; GEM (150āÆĪ¼gāÆL-1); and a combination of AuNPs and GEM (80āÆĪ¼gāÆL-1 AuNPs + 150 Ī¼g L-1 GEM). AuNPs induced DNA damage and increased nuclear abnormalities levels, with coating showing an important role in the toxicity of AuNPs to fish. The combined exposures of AuNPs and GEM produced an antagonistic response, with observed toxic effects in the mixtures being lower than the predicted. The results raise concern about the safety of AuNPs and demonstrate interactions between them and other contaminants.
- Role of oxidative stress-induced systemic and cavernosal molecular alterations in the progression of diabetic erectile dysfunctionPublication . Castela, Angela; Gomes, Pedro; Domingues, Valentina F.; PaĆga, Paula; Costa, Raquel; Vendeira, Pedro; Costa, CarlaBackground Erectile dysfunction (ED) is a prevalent complication of diabetes, and oxidative stress is an important feature of diabetic ED. Oxidative stress-induced damage plays a pivotal role in the development of tissue alterations. However, the deleterious effects of oxidative stress in the corpus cavernosum with the progression of diabetes remain unclear. The aim of this study was to evaluate systemic and penile oxidative stress status in the early and late stages of diabetes. Methods Male Wistar streptozotocin-diabetic rats (and age-matched controls) were examined 2 (early) and 8 weeks (late) after the induction of diabetes. Systemic oxidative stress was evaluated by urinary H2O2 and the ratio of circulating reduced/oxidized glutathione (GSH/GSSG). Penile oxidative status was assessed by H2O2 production and 3-nitrotyrosine (3-NT) formation. Cavernosal endothelial nitric oxide synthase (eNOS) was analyzed by quantitative immunohistochemistry. Dual immunofluorescence was also performed for 3-NT and Ī±-smooth muscle actin (Ī±-SMA) and eNOSāĪ±-SMA. Results There was a significant increase in urinary H2O2 levels in both diabetic groups. The plasma GSH/GSSG ratio was significantly augmented in late diabetes. In cavernosal tissue, H2O2 production was significantly increased in late diabetes. Reactivity for 3-NT was located predominantly in cavernosal smooth muscle (SM) and was significantly reduced in late diabetes. Quantitative immunohistochemistry revealed a significant decrease in eNOS levels in cavernosal SM and endothelium in late diabetes. Conclusions The findings indicate that the noxious effects of oxidative stress are more prominent in late diabetes. Increased penile protein oxidative modifications and decreased eNOS expression may be responsible for structural and/or functional deregulation, contributing to the progression of diabetes-associated ED.
- Determination of chlorfenvinphos in soils by microwave-assisted extraction and stripping voltammetry with an ultramicroelectrodePublication . Morais, Simone; Tavares, Oriza; PaĆga, Paula; Delerue-Matos, CristinaA methodology for the determination of the pesticide chlorfenvinphos by microwave-assisted solvent extraction and square-wave cathodic stripping voltammetry at a mercury film ultramicroelectrode in soil samples is proposed. Optimization of microwave solvent extraction performed with two soils, selected for having significantly different properties, indicated that the optimum solvent for extracting chlorfenvinphos is hexane-acetone (1:1, v/v). The voltammetric procedure is based on controlled adsorptive accumulation of the insecticide at the potential of -0.60 V (vs. Ag/AgCl) in the presence of Britton-Robinson buffer (pH 6.2). The detection limit obtained for a 10 s collection time was 3.0 x 10-8 mol l-1. The validity of the developed methodology was assessed by recovery experiments at the 0.100 Āµg g-1 level. The average recoveries and standard deviations for the global procedure reached byMASE-square-wave voltammetry were 90.2Ā±2.8% and 92.1Ā±3.4% for type I (soil rich in organic matter) and type II (sandy soil) samples, respectively. These results are in accordance to the expected values which show that the method has a good accuracy.