Un método de bajo costo para la determinación de cobre a nivel de vestigios en matrices de interés ambiental por espectrofotometría en fase sólida (EFS)

A method for determining copper by solid phase spectrophotometry (SPS) was optimized using the Doehlert design. Copper(II) was sorbed on a styrene-divinylbenzene anion-exchange resin as a Cu(II)-1-(2-pyridylazo)-2-naphthol (PAN) complex, at pH 7.0. Resin phase absorbances at 560 and 800 nm were measured directly. The detection limit was found to be 2.5 µg L-1. The relative standard deviation on ten replicate determinations of 10 µg Cu(II) in 1000 mL samples was 1.1%. The linear range of the determination was 5.0-100 µg L-1. The method was applied successfully to the determination of Cu(II) in natural water and vegetable samples.

Desenvolvimento e validação de método de análise de glifosato em grãos de soja

The main objective of this work is to develop an efficient procedure to determine glyphosate in soybean grains. The cleanup of the aqueous extracts was done in two steps, beginning with liquid-liquid partitioning and then solid-phase extraction with anion exchange resin. After derivatization with a mixture of trifluoroacetic anhydride (TFAA) and trifluoroethanol (TFE), quantification was done by gas chromatography coupled to mass spectrometry. The mean recovery and RSD of the spiked samples were, respectively, 80.5% and 3.1% at level 0.200 mg kg-1, 93.3% and 18.7% at level 0.500 mg kg-1 and 92% and 3.5% at level 1.000 mg kg-1. The method was linear in the working range (correlation coefficient = 0.9965).

Efeito do triacilglicerídeo de cadeia média, da fibra e do cálcio na disponibilidade de magnésio e de zinco pelo método in vitro e metodologia de superfície de resposta

Nutritional therapy with enteral diets became highly specialized in the last years. This work aims to study the effect of the components of a formulation, namely fiber, calcium and medium-chain triglycerides, for dialysability of minerals. Analysis of multiple variables was done using response surface methodology. The level curve showed that the tertiary interaction MCT-fiber-calcium was the one that presented the highest synergism in the formulation. The proportion of 33% MCT, 25% fiber and 42% calcium, gave the best formulation for availability of magnesium.

Ondas ultrassônicas e pérolas de vidro: um novo método de extração de beta-galactosidase para uso em laboratório

The optimization of a traditional technique of cellular disruption by abrasion was carried out and a process using ultrasonic waves associated with glass pearls to extract beta-galactosidase from Kluyveromyces marxianus proposed. In the first case, the effects of the diameter and weight of the pearls in relation to the volume of cellular suspension and amount of time for cellular disruption were evaluated. The efficiency of the new process of cellular disruption was evaluated by varying the length of time of sonification and comparing with the method of abrasion under the same conditions. The proposed method can be efficiently applied to obtain beta-galactosidase at laboratory scale.

Síntese de padrões cromatográficos e estabelecimento de método para dosagem da composição de ésteres de ácidos graxos presentes no biodiesel a partir do óleo de babaçu

Several alkyl esters were synthesized, purified, characterized by ¹H NMR and employed as standards for establishing chromatographic methods to monitor their formation in the synthesis of biodiesel. The efficiency of the chromatographic methods was confirmed with the products of enzymatic transesterification of babassu oil with different alcohols (C2 to C4), using Lipozyme as catalyst.

Altered nitrogen balance and decreased urea excretion in male rats fed cafeteria diet are related to arginine availability

Hyperlipidic diets limit glucose oxidation and favor amino acid preservation, hampering the elimination of excess dietary nitrogen and the catabolic utilization of amino acids.We analyzed whether reduced urea excretion was a consequence of higherNO ; (nitrite,nitrate, and other derivatives) availability caused by increased nitric oxide production in metabolic syndrome. Rats fed a cafeteria diet for 30 days had a higher intake and accumulation of amino acid nitrogen and lower urea excretion.There were no differences in plasma nitrate or nitrite. NO and creatinine excretion accounted for only a small part of total nitrogen excretion. Rats fed a cafeteria diet had higher plasma levels of glutamine, serine, threonine, glycine, and ornithinewhen comparedwith controls,whereas arginine was lower. Liver carbamoyl-phosphate synthetase I activity was higher in cafeteria diet-fed rats, but arginase I was lower. The high carbamoyl-phosphate synthetase activity and ornithine levels suggest activation of the urea cycle in cafeteria diet-fed rats, but low arginine levels point to a block in the urea cycle between ornithine and arginine, thereby preventing the elimination of excess nitrogen as urea. The ultimate consequence of this paradoxical block in the urea cycle seems to be the limitation of arginine production and/or availability.

Uma abordagem simplificada do método Monte Carlo Quântico: da solução de integrais ao problema da distribuição eletrônica

The paper presents an introductory and general discussion on the quantum Monte Carlo methods, some fundamental algorithms, concepts and applicability. In order to introduce the quantum Monte Carlo method, preliminary concepts associated with Monte Carlo techniques are discussed.

Dinámica del heleoplancton en relación a las fluctuaciones hidrológicas en aiguamolls de l’Empordà (NE de la península Ibérica). Propuesta de un método sencillo de monitorización basado en la abundancia de grupos taxonómicos

Monitoring of the 'ecological water quality' in 'Aiguamolls de l’Empordà' Natural Park was carried out between September 1996 and August 1997 . The aim of this sampling programme was to design a simple method for rapid detect changes in water quality due to human activity. These include flow regulation by the Park management, nutrient entries from effluents of a nearby wastewater treatment plant or agricultural fertilising. The proposed method is based on the analysis of the abundance of characteristic taxonomic groups of aquatic invertebrates (heleoplankton). The simplicity of the method is ensured by the use of large taxa which are easier to recognise than species. The functioning of aquatic systems has been modelled by means of correspondence analysis between samples and taxa. Results can be summerized in five environmental conditions with a regular community structure. Dominated by one taxon: cladocerans, ostracods, calanoids, cyclopoids and harpacticoids. The dynamics of both freshwater and brackish lagoons can be modelled as displacements between these five groups of environmental conditions. Nevertheless, the “calanoids situation” and the “harpacticoids situation” occur mainly in brackish lagoons, whereas the “cladocerans situation” occurs mainly in freshwater. The four principal axes of data variation have been respectively identified as nutrient turnover rate, hypertrophy, degree of mineralization of the organic matter and eutrophy. The use of these taxa has been validated by comparison with a model obtained from the species. We conclude that in a highly fluctuating system such as the one here, only persistent situations of eutrophy or hypertrophy must be equated to low 'ecological water quality'

Desenvolvimento e validação de método analítico para determinação simultânea de lamivudina, zidovudina e nevirapina em comprimidos dose-fixa combinada por cromatografia líquida de alta eficiência

An analytical method has been developed and validated for the quantitation of lamivudine, zidovudine and nevirapine in the fixed-dose combination film-coated tablet by high performance liquid chromatography, in accordance with RE No. 899/2003, National Sanitary Surveillance Agency. It was based on an isocratic elution system with a potassium phosphate buffer pH 3.0: acetonitrile (60:40 v/v) mobile phase, C18, 250 x 46 mm column, 10µm particle size, λ 270 nm. The statistically evaluated results have shown that the method is specific, precise, accurate, and robust, ensuring the analytical safety of 3TC, AZT and NVP determination, which emerges as a new therapeutic alternative for antiretroviral treatment.

Fitodisponibilidad de Cd en suelo de diferente pH tratado con lodo albañal estimada por método isotópico y extracción química

The Cd phytoavailability in sewage sludge-amended soils of different pHs using the 109Cd L-value isotopic method and Cd extracted by DTPA has been determined. Maize plants (Zea mais L.) were grown under greenhouse conditions in a xanthic ferralsol at different pHs amended with five sewage sludge (SS) rates, and labeled with 74 kBq kg-1 of 109Cd. The SS rates altered the properties of the soil chemicals and these influenced the isotopic parameter (L-value) and percent of Cd uptake by plants from soil (%Cdpdfs) and SS (%CdpdfSS). L-values and Cd extracted by DTPA correlate significantly with SS rates and Cd uptake by plants and are efficient for predicting the Cd phytoavailability in the sewage sludge-amended soil.

Otimização de método para determinação de flavonóis e flavonas em frutas por cromatografia líquida de alta eficiência utilizando delineamento estatístico e análise de superfície de resposta

This work optimized the HPLC conditions for the simultaneous determination of luteolin, apigenin, myricetin, quercetin and kaempferol in aglycone form, as well defined the best conditions for hydrolysis/extraction of these flavonoids in fruits, using the statistical central composite design and response surface analysis. A reverse phase method was developed using a gradient of methanol/water acidified with 0.3% formic acid as mobile phase and a photodiode array detector. The samples were extracted with methanol/water (50:50 v/v) at 90 ºC. The optimum time and HCl concentration varied for the different fruits investigated, demonstrating the necessity of optimizing these conditions for each fruit analyzed. Good recovery (87.1 to 96.3%), repeatability and linearity were obtained.

Entalpía de disolución de sulfacetamida sódica en agua: comparación entre la calorimetría isoperibólica de solución y el método de van't Hoff

The dissolution enthalpy (ΔH0soln) of sodium sulfacetamide in water was determined by means of isoperibolic solution calorimetry. It was found that ΔH0soln diminishes as the drug concentration increases. Otherwise, the calorimetric values obtained as a function of the drug concentration were significantly different than those predicted by the van't Hoff method. It was demonstrated that the later is not a fully reliable method for the determination of ΔH0soln values in the specific case of highly soluble sodium salts. The observed phenomenon could be explained by the presence of strong solute-solute interactions at high salt concentrations, in addition to solute-solvent and solvent-solvent interactions.

Desenvolvimento e validação de método por cromatografia líquida de alta eficiência para determinação simultânea das impurezas timina e timidina na matéria-prima estavudina

A HPLC method was developed to quantify thymine and thymidine impurities in stavudine bulk drug. The separation was carried out in isocratic mode using methanol/water (20:80) as mobile phase, a C18 column and UV detection at 266 nm. The method provided selectivity based on peak purities and resolution among peaks. It was linear over the range of 0.5-5.0 µg/mL. The quantitation limits were 0.021 µg/mL for thymine and 0.134 µg/mL for thymidine. The average accuracies of three concentrations ranged from 97.06 to 102.61% and precision was close to 1%. The method showed robustness, remaining unaffected by deliberate variations in relevant parameters.

Obtenção de filmes finos de TiO2 nanoestruturado pelo método dos precursores poliméricos

This work focuses in optimizing setup for obtaining TiO2 thin films by polymeric precursor route due to its advantages on stoichiometric and morphological control. Precursor stoichiometry, synthesis pH, solids concentration and rotation speed at deposition were optimized evaluating thin films morphology and thickness. Thermogravimetry and RMN were applied for precursor's characterization and AFM, XRD and ellipsometry for thin films evaluation. Results showed successful attainment of homogeneous nanocrystalline anatase TiO2 thin films with outstanding control over morphological characteristics, mean grain size of 17 nm, packing densities between 57 and 75%, estimated surface areas of 90 m²/g and monolayers thickness within 20 and 128 nm.

Desenvolvimento e validação de um método analítico rápido por cromatografia líquida de alta eficiência para determinação de nimesulida em estudos de liberação in vitro

A high performance liquid chromatography (HPLC) method has been developed for a rapid determination of nimesulide in dissolution studies. Nimesulide was analyzed using 5 µm Lichrospher® RP-18 column (125 x 4 mm i.d.) and mobile phase acetonitrile: phosphate buffer pH=6.0 (55:45) at a flow-rate of 1.0 mL min-1. Detection was carried out at 300 nm at 25 ºC. The method was applied to analysis of nimesulide in in vitro release studies and showed a rapid and efficient analytical alternative for evaluation of dissolution profile of nimesulide.