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- Effect of arsenic, lead and zinc on seed germination and plant growth in black nightshade (solanum nigrum l.) vs. clover (trifolium incarnatum l.)Publication . Marques, Ana P. G. C.; Rangel, António O. S. S.; Castro, Paula M. L.S. nigrum was found to proliferate in sediments with high levels of metal pollution. Toxicity tests were performed using seed germination, root elongation, shoot length and biomass as parameters for establishing growth inhibition of S. nigrum and T. incarnatum by arsenic, lead and zinc. All the elements had a higher inhibitory action on the ger-mination and growth of T. incarnatum – inhibition occur-ring at 3 mg element per kg of dry sand. S. nigrum presented germination and growth at higher concentrations of those elements - 7 mg Pb kg-1, 10 mg Zn kg-1 and 10 mg As kg-1. Although inhibitory concentrations for each plant were dif-ferent, increasing the elements concentration reduced seed germination, root elongation and shoot length in T. incar-natum, but not always in S. nigrum. For the latter, low con-centrations (3 mg kg-1 dry sand) of Zn and As seemed to have stimulatory effects on germination. The addition of nu-trients did not cause a significant (P < 0.05) difference in the germination of both plants, except for high metal/ metal-loid concentration in S. nigrum. Concerning growth char-acteristics, nutrient addition was only a differentiation factor for shoot length at low metal/metalloid concentrations. S. nigrum could be a promising plant to be used in further ex-periments concerning the potential of phytoremediation of metal contaminated sites, as long as an adequate planting strategy is followed.
- A sequential injection fluorimetric methodology with in-line solid phase extraction for biogenic amines screening in waterPublication . Ribas, Tânia C. F.; Tóth, Ildikó V.; Rangel, António O. S. S.A method for the screening of biogenic amines in waters, whose presence at some concentration levels potentially cause adverse effects on humans, was developed for the first time. A suitable and easy to operate system, with low reagent consumption was devised. The proposed flow-based system was divided into two analytical parts, preconcentration and derivatization of the biogenic amines. Solid phase extraction, using a Chelex 100 resin, was the newly chosen strategy for preconcentration of the analyte and also removal of possible matrix interferences. Fluorescamine was used as derivatization reagent for biogenic amines followed by fluorimetric detection. The influence of different sorbent materials for preconcentration and flow system parameters such as pH of standards and buffer, composition of the eluent solution, flow-rates, standard/sample volume, were studied. The interference of ammonia was assessed, and no interference was observed. The limits of detection and quantification were 1.7 and 5.6 µmol L−1, respectively. The developed system was applied to water samples and the recovery results were 98 ± 7%.
- Construction and use of a tubular picrate ion-selective electrode for reducing sugar determination in Port wine by flow-injection analysisPublication . Lopes, Teresa I. M. S.; Rangel, António O. S. S.; Lima, José L. F. C.; Montenegro, M. Conceição B. S. M.A picrate ion-selective electrode without inner reference solution and based on bis(triphenylphosphoranylidene)ammonium picrate dissolved in 2-nitrophenyloctyl ether was constructed and its characteristics assessed. With respect to reducing sugar determination in Port wine, a tubular electrode based on the same sensor system was developed and incorporated into a flow-injection manifold devised for this determination. The methodology involves a reaction between the reducing sugar and picric acid, the decrease in the picrate concentration being monitored with the tubular electrode. A linear dependence between peak width, at a fixed potential and the logarithm of sugar concentration in the range 25–200 g l−1 was obtained. The proposed system allows wine samples to be injected with no previous treatment and allows a sample throughput of 50 determinations per hour, a relative standard deviation less than 4%, and the results are comparable to the reference procedures.
- Sequential injection determination of nitrate in vegetables by spectrophotometry with inline cadmium reductionPublication . Oliveira, Sara M.; Lopes, Teresa I. M. S.; Rangel, António O. S. S.A sequential injection system for the determination of nitrate (NO3 2) in vegetables was developed to automate this determination, allowing for substantially reduced reagent consumption and generated waste using low-cost equipment. After extraction with water and filtration, the extracted nitrate is reduced inline to nitrite in a copperized cadmium (Cd) column and determined as nitrite. According to the Griess–Ilosvay reaction, nitrate is diazotized with sulfanilamide and coupled with N-(1-naphtyl)-ethylenediamine dihydrochloride to form a purple-red azo dye monitored at 538 nm. Nitrate can be determined within a range of 1.35–50.0 mg L21 of NO3 2 (corresponding to 0.270–10.0 g of NO3 2 per kg of vegetable), with a conversion rate of nitrate to nitrite of 99.1+0.8%. The results obtained for 15 vegetable extracts compare well with those provided by the classical procedure, with a sampling throughput of 24 determinations per hour and relative standard deviations better than 1.2%.
- Evaluation of different substrates in constructed wetlands planted with Typha latifolia for the treatment of tannery wastewaterPublication . Calheiros, Cristina S. C.; Rangel, António O. S. S.; Castro, Paula M. L.
- Ecotechnologies as urban solutions for sustainable water managementPublication . Calheiros, Cristina S. C.; Monteiro, Cristina M.; Rangel, António O. S. S.; Castro, Paula M. L.
- Assessment of the impact synthetic Fe(III)-chelates amendment in soil microbial community dynamicsPublication . Machado, Ana; Mesquita, Letícia S.; Rangel, Maria; Mesquita, Raquel B. R.; Rangel, António O. S. S.; Bordalo, Adriano A.
- Raoultella ornithinolytica: an opportunistic pathogen in the oral cavity of chronic kidney disease patientsPublication . Costa, Carolina F. F. A.; Campos, Carla; Merino, Ana; Silva, Nádia; Mesquita, Raquel B. R.; Rangel, António O. S. S.; Sampaio-Maia, Benedita
- Determination of mercury in fish by cold vapor atomic absorption spectrophotometry using a multicommuted flow Injection analysis systemPublication . Silva, M. Fátima; Tóth, Ildikó V.; Rangel, António O. S. S.A flow system was developed for the determination of total mercury concentration in fish samples by cold vapor atomic absorption spectrophotometry (CVAAS), based on the multicommuted flow injection analysis (MCFIA) approach. The system uses independently controlled solenoid valves for the introduction of reagents and samples. When not injected, solutions were recirculating to the reservoir bottles, in this way reducing the waste produced by the analytical system and also the sample consumption. Results were compared to those obtained by the reference flow injection procedure. Accuracy was also assessed by recovery studies using a certified reference material as well as spiked samples; recovery percentages in the range of 90.7% to 99.8% were found. The repeatability of the method was better than 6.0% (RSD, n = 10). A limit of detection of 4.8 μg of mercury per kg of fresh fish sample was achieved. The total waste produced was reduced to 30% of that from the reference flow injection CVAAS procedure.
- Sequential injection system for the spectrophotometric determination of ammonium in Portuguese estuarine watersPublication . Segundo, Ricardo L. A.; Mesquita, Raquel B. R.; Ferreira, M. Teresa S. O. B.; Teixeira, Catarina F. C. P.; Bordalo, Adriano A.; Rangel, António O. S. S.