Avaliação de filtros domésticos comerciais para purificação de águas e retenção de contaminantes inorgânicos

Twenty domestic commercial filters, in order to determine the percentual retention of color, turbidity, dry residue, bicarbonates, carbonates, total hardness, nitrogens, iron, chlorides, fluorides, and residual chlorine (parameters of food legislation) and sulphides in thirteen water samples proceeding from springs, wells, rivers, lakes, drinking patterns and standards, before and after purification were evaluated. The results showed that purifiers presented adequate retention for nitrates (74.8 ± 16.2 %) and residual chlorine (74.0 ± 11.2) and medium retention for sulphides (61.7 ± 11.3); while porcelain plus activated carbon filters presented adequate retention for color (90.0 ± 19.7), turbidity (76.4 ± 18.4) and iron (83.5 ± 15.1). Therefore the retention of carbonates, bicarbonates, total hardness, chlorides, dry residue, fluorides, ammonium nitrogens and nitrites was less than 10%, and the values of pH didn't show significant variation, for all the filters studied.

A natureza das substâncias de referência na avaliação de massas molares de resinas PBLH por meio de cromatografia de exclusão por tamanho e osmometria de pressão de vapor

The SEC and VPO behaviour of hydroxyl-terminated polybutadiene resins was investigated using toluene as solvent and polybutadiene and polystyrene as standards. The results show that molar mass obtained depend on the nature of the standards used in the calibration, specialy in SEC analysis.

Avaliação quantitativa de cardenolídeos no cultivar experimental de Digitalis lanata do maciço do itatiaia e perspectivas de seu emprego industrial

The content of digoxin and lanatoside C (jointly quantified), lanatoside A, lanatoside B, glucoevatromonoside, odorobioside G, glucogitoroside, glucoverodoxine, glucodigifucoside and digitalinum verum was determined by HPLC in Digitalis lanata harvested in Brazil, as well as in clones industrially employed for the production of cardenolides. The Brazilian plants presented greater variation in the contents of cardenolides than the analyzed clones. Lanatoside C and digoxin concentrations were higher in the clones (6120±640 nmol/g dry leaf) than in the Brazilian plants (1820±900 nmol/g dry leaf). The concentrations of these glycosides were found to be within the range described for native species and also were similar to an European cultivar, what makes possible its industrial use for the cardenolides production.

Construção e avaliação de um eletrodo tubular sensível ao íon hidrogênio como detector em sistemas de análise em fluxo

The construction of a tubular hydrogen ion-selective potentiometric electrode without inner reference solution, based on the tridodecylamine (TDDA) ionophore, and its evaluation in a flow system are described. TDDA was dissolved in 2-nitrophenyl octyl ether, dispersed in a PVC membrane and applied directly to a conducting support which consisted of an epoxy resin and graphite mixture. The electrode was designed with a tubular geometry to effort facilities to be coupled as part of a flow injection network. The main working characteristics such as response time, linear pH range, selectivity and life time were evaluated and compared with those obtained which a conventionally shaped electrode based on the same sensor. The electrode showed a slope of 51-52 mV dec-1 within a linear pH range from 4.0 up to 12.0.

Métodos para avaliação do grau de oxidação lipídica e da capacidade antioxidante

In this work several methods for evaluation of the degree of lipid oxidation and antioxidant activity are reviewed. Some aspects related to the recent advances mentioned in the literature are also reported.

Avaliação quimiométrica da distribuição de metais pesados em composto de lixo urbano domiciliar

The main obstacle to the use of compost from urban waste in agriculture is the presence of heavy metals. Once in the soil, their effect is accumulative and they may contaminate crops and water. The present study reports the evaluation of the chemical distributions of Cu, Pb, Mn and Zn in three different sized fractions (unsieved, < 1,18mm and > 1,18mm) of compost, by means of a sequencial extraction procedure and a chemometric analysis of the total content of all metals in each fraction. The pattern recognition methods showed significant differences in total heavy metal contents for the different fractions. The finest one was the most contaminated. Meanwhile, this fraction presented lower amounts of metals in avaliable forms. This behavior can be attributed to the presence of metal particles in their elemental states in this fraction.

Síntese de 1,3,5-triazinas substituídas e avaliação da toxicidade frente a Artemia Salina leach

The synthesis of ten symmetrically and unsymmetrically substituted 1,3,5-triazines by Phase Transfer Catalysis (PTC) method is described. Their toxicities were determined against Artemia salina Leach. The LD50 values have also been obtained for these compounds.

Avaliação da fitodisponibilidade de cádmio, chumbo e crômio, em soja cultivada em latossolo vermelho escuro tratado com fertilizantes comerciais

The aim of this work was to evaluate the availability of the toxic heavy metals: cadmium, lead and chromium, in soybean, from some fertilizers. Five fertilizers and soluble salts contend Cd, Pb and Cr were used. All the treatments were accomplished in vases of 2,5 L with application of two doses, 50 and 100 kg.ha-1 for the fertilizers and 25 and 50 kg.ha-1 for the salts.

Avaliação da capacidade tamponante - um experimento participativo

The aim of this work is to show an experiment from which students can learn some of the main characteristics of buffer solutions. A mixture of some acid-base indicators, named as Yamada's indicator, can be used to estimate pH values in an acid-base titration of a buffer, with good approximation. In the experiment it is also possible to verify the relationship between the buffer capacity and the concentrations and the molar ratio of the components of a NH3 / NH4+ buffer solution. The shortage of experiments associated with the relative small importance given to many aspects of buffer solutions, is now explored with simplicity. In the proposed experiments, students prepare buffer solutions by themselves, calculate the pH, understand how acid-base indicators act and learn how buffer solutions work through graph constructed by sharing experimental data.

Avaliação da salinização de açudes no semi-árido brasileiro por ICP-AES

The salt accumulation process in some reservoirs of regular and irregular use (from 10 to 50 years of constrution), located in the Southeast of Bahia State was evaluated. Inductively coupled plasma atomic emission spectrometry was used to evaluate the concentrations of Na, K, Ca and Mg in water samples from inside and upstream of the reservoirs. The results showed that for reservoirs of irregular use, the salt accumulation, indicated by the tracer Na, increases with the age of the reservoirs, however for the reservoirs of regular use the hydraulic retention time is the main parameter.

Avaliação do uso de métodos quimiométricos em análise de solos

One of the major interests in soil analysis is the evaluation of its chemical, physical and biological parameters, which are indicators of soil quality (the most important is the organic matter). Besides there is a great interest in the study of humic substances and on the assessment of pollutants, such as pesticides and heavy metals, in soils. Chemometrics is a powerful tool to deal with these problems and can help soil researchers to extract much more information from their data. In spite of this, the presence of these kinds of strategies in the literature has obtained projection only recently. The utilization of chemometric methods in soil analysis is evaluated in this article. The applications will be divided in four parts (with emphasis in the first two): (i) descriptive and exploratory methods based on Principal Component Analysis (PCA); (ii) multivariate calibration methods (MLR, PCR and PLS); (iii) methods such as Evolving Factor Analysis and SIMPLISMA; and (iv) artificial intelligence methods, such as Artificial Neural Networks.

Avaliação dos métodos analíticos para a determinação de metabólitos do benzeno como potenciais biomarcadores de exposição humana ao benzeno no ar

Increasing attention is being paid to the use of biomarkers for determining the exposure of humans to air toxics. Biomarkers include the nonreacted toxic substance, their metabolites, or the reaction products of these toxics with naturally substances in the body. Significant progress has been made in the measurement of biomarkers during the past several years. Much of this progress has been because of the development of advanced analytical techniques for identification and quantification of the chemical species in complex matrix, such as biological fluids. The assessment of the potential cancer risk associated with exposure to benzene at occupational and non-occupational ambient is necessary because of the toxicological implications of this air pollutant. Thus, in this review, the analytical methodologies used to determine the benzene metabolites, in special, urinary muconic acid and S-phenylmercapturic acid, are described and several problems affecting the precision of these procedures are discussed. Finally, in view of the difficulty pointed out for selecting the more adequate biomarker, further studies to evaluate the human exposure levels to benzene should be done.

Avaliação da contaminação humana por hidrocarbonetos policíclicos aromáticos (HPAs) e seus derivados nitrados (NHPAs): uma revisão metodológica

Polycyclic aromatic hydrocabons (PAHs) and their nitroderivatives (NPAHs) are ubiquitous in the environment and they are produced in several industrial and combustion processes. Some of these compounds are potent carcinogens/mutagens and their determination in biological samples is an important step for exposure control. A review of the analytical methodologies used for the determination of PAHs and their metabolites in biological samples is presented.