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Química Nova, Volume: 29, Número: 5, Publicado: 2006
  • Editorial

    Mangrich, Antonio S
  • Determinação de nitrato e nitrito em chás de peles de pescados empregados para tratamento de asma brônquica na região sul do Rio Grande do Sul Artigo

    Bastos, Ademir Larrea; Baisch, Ana Luiza Muccilo; Soares, Leonor Almeida de Souza; Burkert, Janaína Fernandes de Medeiros; Furlong, Eliana Badiale

    Resumo em Inglês:

    The objective of this paper was to determine nitrate and nitrite anions in toasted fish skin tea, which the population of southern Rio Grande do Sul believes to have pharmacological properties for trating asthma. Two methods were compared, an official and one described by Guozhen et al., that has the advantage of not needing reduction of nitrate to nitrite on a Cd column. The samples were the skin of the fish species Balistes capriscus (peixe porco) and Menticirrhus littoralis (papa-terra), both crude and toasted, as traditionally used. The method of Guozhen et al. was used due to its performance (detection limit 0.005 µmol/L NO3- and 0.02 µmol/L - NO2- and mean recuperation of 100 and 97% respectively for each anion) and results similar to those of the official methods under conditions used by the population, the estimated daily intake, of the teas is equivalent to 0.03 to 0.05 mg of nitrate and 0.007 to 0.014 mg of nitrite. These values are in accord with safety recommendations and don't represent a health risk.
  • Aspectos físico-químicos e biológicos relacionados à ocorrência de Biomphalaria glabrata em focos litorâneos da esquistossomose em Pernambuco Artigo

    Silva, Petronildo Bezerra da; Barbosa, Constança Simões; Pieri, Otávio; Travassos, Antônio; Florencio, Lourdinha

    Resumo em Inglês:

    This study analyzes the physico-chemical and biological parameters of freshwater aquatic environments in coastal areas of the State of Pernambuco, Brazil, where snail vector foci and cases of schistosomiasis have been recorded. The tests were carried out using standard methods and sediments were analyzed using the X-ray fluorescence technique. The micro-algae were analyzed using conventional microscopy. The most abundant chemical elements in the sediments were Fe, Ca, Si and Al and there were high concentrations of electrolytes in comparison with data published in the literature. The mean values for salinity (7.7 g/L) and sulfate (489 mg/L) were much higher than normal for freshwater environments. The micro-algae identified are those that inhabit environments with higher levels of salinity. The snail Biomphalaria glabrata seems, therefore, to be more tolerant to salty environments and this constitutes a risk of spread of schistosomiasis.
  • Atividade antioxidante de óleos essenciais de espécies de Croton do nordeste do Brasil Artigo

    Morais, Selene Maia de; Catunda Júnior, Francisco Eduardo Aragão; Silva, Ana Raquel Araújo da; Martins Neto, Jason Stone; Rondina, Davide; Cardoso, José Henrique Leal

    Resumo em Inglês:

    Three Croton species, C. zenhtneri, C. nepetaefolius and C. argyrophylloides, were collected at two different times, 6:00 and 13:00 h, their essential oils were extracted by steam distillation and analyzed by gas Chromatography / Mass Spectrometry. The percentage yield of oil constituents changes along the day. The oils were submitted to the antioxidant test thiobarbituric acid reactive species, using BHT and a-tocoferol as the reference compounds. All oils exhibited good antioxidant activities. In general, C. zenhtneri and C. argyrophylloides essential oils showed higher antioxidant activity than C. nepetaefolius.
  • Análises quali- e quantitativa de cafés comerciais via ressonância magnética nuclear Artigo

    Tavares, Leila Aley; Ferreira, Antonio Gilberto

    Resumo em Inglês:

    Coffee is one of the beverages most widely consumed in the world and the "cafezinho" is normally prepared from a blend of roasted powder of two species, Coffea arabica and Coffea canephora. Each one exhibits differences in their taste and in the chemical composition, especially in the caffeine percentage. There are several procedures proposed in the literature for caffeine determination in different samples like soft drinks, coffee, medicines, etc but most of them need a sample workup which involves at least one step of purification. This work describes the quantitative analysis of caffeine using ¹H NMR and the identification of the major components in commercial coffee samples using 1D and 2D NMR techniques without any sample pre-treatment.
  • Influência da espessura nas propriedades de absorção e emissão e na morfologia de filmes automontados de poli(p-fenileno vinileno) Artigo

    Piovesan, Erick; Hidalgo, Ángel Alberto; Marletta, Alexandre; Vega, Maria Leticia; Ruggiero, Reinaldo

    Resumo em Inglês:

    In this report, we studied the thickness effect on the optical and morphological properties of self-assembled (SA) poly(p-phenylenevinylene) (PPV) films, wich were processed with 5 and 75 layers from a PPV precursor polymer and dodecylbenzenesulfonate, and then, thermally converted at 230 °C. The increase of the film thickness yielded more intense peaks in the vibrational spectral range. The electron-phonon coupling was quantified by the Huang - Rhys factor, that shows the effects on the polymer chain mobility in the interface substrate/polymer. A strong emission anisotropy r=0.57 was observed for the film with 5 layers of thickness decreasing to 0.34 for the film with 75 layers. Finally, the surface topology of the films was measured using Atomic Force Microscopy.
  • Efeito dos ácidos hexenurônicos e da lignina no desempenho da ozonólize, em diferentes pHs da reação Artigo

    Ventorim, Gustavo; Colodette, Jorge Luiz

    Resumo em Inglês:

    The effect of pH on the performance of the ozonolysis stage in pulp production was evaluated for conventional and acid treated brown and oxygen delignified eucalyptus kraft pulps. The objective was to determine separately the effects of lignin and hexenuronic acid on the performance of the ozonolysis stage. The reaction of ozone with hexenuronic acid is less sensitive to pH than the reaction of ozone with lignin. The efficiency and the selectivity of the reaction of ozone with pulp decreases after removal of hexenuronic acids. Increasing up to 7.0 the pH during the ozonolysis is viable in the sequence Z/D(EOP)D, resulting in savings of H2SO4 (8,5 kg/tsa) and NaOH (5 kg/tsa), but is not recommended in the sequence Z/ED(PO).
  • Determinação simultânea de resíduos de cloranfenicol, tianfenicol e florfenicol em leite bovino por cromatografia eletrocinética micelar Artigo

    Pezza, Leonardo; Ríos, Àngel; Nozal, Leonor; Arce, Lourdes; Valcárce, Miguel

    Resumo em Inglês:

    A micellar electrokinetic chromatographic method (MEKC) is described for determining residues of amphenicols(chloramphenicol,thiamphenicol and florfenicol) in bovine milk. MEKC is conducted by using a separation buffer consisting of 20 mM Na2HPO4, 10 mM Na2B4O7, 50 mM SDS at pH 8.0; UV detection at 210 nm and 10 kV of voltage. The limit of detection ranged from 4.3-5.3 µg L-1. The MEKC method was applied for the simultaneous determination of amphenicols in milk samples spiked with amphenicols at three concentration levels: 10, 30 and 50 µg L-1. Recoveries ranging from 91-105% were obtained by following a simple extraction/preconcentration procedure.
  • Construção e aplicação de biossensores usando diferentes procedimentos de imobilização da peroxidase de vegetal em matriz de quitosana Artigo

    Oliveira, Inês Rosane Welter Zwirtes de; Vieira, Iolanda Cruz

    Resumo em Inglês:

    Biosensors were developed by immobilization of gilo (Solanum gilo) enzymatic extract on chitosan biopolymers using three different procedures: glutaraldehyde, carbodiimide/glutaraldehyde and epichlorohydrin/glutaraldehyde. The best biosensor performance was obtained after the immobilization of peroxidase on chitosan with epichlorohydrin/glutaraldehyde. Linear analytical curves for hydroquinone concentrations from 2.5x10-4 to 4.5x10-3 mol L-1 with a detection limit of 2.0x10-6 mol L-1 and recovery of hydroquinone ranging from 95.1 to 105% were obtained. The relative standard deviation was < 1.0 % for a solution of 3.0x10-4 mol L-1 hydroquinone and 2.0x10-3 mol L-1 hydrogen peroxide in 0.1 mol L-1 phosphate buffer solution at pH 7.0 (n=8). The lifetime of this biosensor was 6 months (at least 300 determinations).
  • O emprego da termogravimetria para determinar a energia de ativação do processo de combustão de óleos combustíveis Artigo

    Leiva, Cecilia Rocío Morales; Crnkovic, Paula Manoel; Santos, Antonio Moreira dos

    Resumo em Inglês:

    Activation energy (Ea) is a parameter that can be applied to make predictions about the quality of oils to be used in an ICO engine. In this study, Ea was determined by thermogravimetry following two different procedures: ASTM E 1641 and Model-free kinetics. The energies were calculated in the low temperature oxidation (LTO) region for three Brazilian fuel oils (denominated A, B and C) and the results were equal using both methods: 43 kJ mol-1 (alpha=0.1 to 0.9) for oil A, 48 kJ mol-1 (alpha=0.1 to 0.5) and 65 kJ mol-1 (alpha=0.5 to 0.9) for oil B, and 58 kJ mol-1 (alpha=0.1 to 0.5) and 65 kJ mol-1 (alpha=0.5 to 0.9) for oil C. It was concluded that, among the oils studied, sample A was potentially the best option concerning the behavior in the LTO region.
  • Preparative separation of flavonoids from the medicinal plant Davilla elliptica St. Hill. by high-speed counter-current chromatography

    Rinaldo, Daniel; Silva, Marcelo Aparecido; Rodrigues, Clenilson Martins; Calvo, Tamara Regina; Sannomiya, Miriam; Santos, Lourdes Campaner dos; Vilegas, Wagner; Kushima, Hélio; Hiruma-Lima, Clélia Akiko; Brito, Alba Regina Monteiro de Souza

    Resumo em Inglês:

    High-speed counter-current chromatography (HSCCC) is a major tool for the fast separation of natural products from plants. It was used for the preparative isolation of the flavonoid monoglucosides present in the aerial parts of the Davilla elliptica St. Hill. (Dilleniaceae). This species is used in Brazilian folk medicine for the treatment of gastric disorders. The optimum solvent system used was composed of a mixture of ethyl acetate-n-propanol-water (140:8:80, v/v/v) and led to a successful separation of quercetin-3-O-alpha-L-rhamnopyranoside and myricetin-3-O-alpha-L-rhamnopyranoside in approximately 3.0 hours with purity higher than 95%. Identification was performed by ¹H NMR, 13C NMR and HPLC-UV-DAD analyses.
  • Método multirresíduo para monitoramento de contaminação ambiental de pesticidas na região de Bauru (SP) usando mel como bio-indicador Artigo

    Rissato, Sandra Regina; Galhiane, Mário Sérgio; Knoll, Fátima do Rosário Naschenveng; Andrade, Rita Mickaela Barros de; Almeida, Marcos Vinícius de

    Resumo em Inglês:

    The presence of residues of the major groups of pesticides (organohalogen, organophosphorous, pyrethroids and organonitrogen) in representative samples of honey produced in Bauru (state of São Paulo, Brazil) was investigated from 1999 through2004. A multiresidue method was applied to honey samples to determine 48 pesticides with recoveries ranging from 76 to 95%. The limits of detection found were lower than 10 µg/kg for GC-MS-SIM. The results indicated that most pesticides found in the samples belonged to the organohalogen and organonitrogen groups. Residues of malathion were detected in almost all of the samples in high concentration.
  • Otimização das condições de produção de ésteres etílicos a partir de óleo de peixe com elevado teor de ácidos graxos ômega-3 Artigo

    Moura, Juliana Maria Leite Nóbrega de; Gonçalves, Lireny Aparecida Guaraldo; Grimaldi, Renato; Soares, Marinalda da Silva; Ribeiro, Ana Paula Badan

    Resumo em Inglês:

    The production of ethyl esters by alcoholysis is an alternative for splitting triacylglycerols due to the possibility of using low temperatures, which results in oxidative protection of the polyunsaturated fatty acids. Ethyl esters produced under mild conditions of temperature could be used as substrate for obtaining structured lipids. The reaction parameters of production of ethyl esters from fish oil with high content of omega-3 fatty acids by alcoholysis were optimized using response surface methodology. An experimental design (2³) (with levels +1 and -1, six axial points with levels -alpha and +alpha and three central points) was applied. The variables investigated were concentration of catalyst, amount of ethyl alcohol and temperature. Ethyl ester conversion was monitored by high performance size exclusion chromatography (HPSEC) and the best result obtained was 95% conversion rate. The optimal conditions were 40 °C, 1% of NaOH and 36% of ethanol.
  • Comportamento de zinco e manganês de pilhas alcalinas em uma coluna de solo Artigo

    Agourakis, Demetrios Chiuratto; Camargo, Iara Maria Carneiro de; Cotrim, Marycel Barboza; Flues, Marlene

    Resumo em Inglês:

    The aim of this study was to evaluate the behavior of Zn and Mn in a soil column. Two soil columns were sampled, and four opened alkaline batteries were placed at the top of one soil column. An acid-rainwater solution (HNO3 and H2SO4; pH 4) was percolated through the battery contaminated column during one year. The results showed that the leaching of alkaline batteries caused enrichment of 70 and 11 times in the Zn and Mn concentration of the topsoil, respectively. Additionally, leaching of electrolyte (KOH) from the batteries increased the soil pH in the contaminated column.
  • Efeito do processo de descafeinação com diclorometano sobre a composição química dos cafés arábica e robusta antes e após a torração Artigo

    Toci, Aline; Farah, Adriana; Trugo, Luiz Carlos

    Resumo em Inglês:

    The decaffeinated coffee market has been expanding increasingly in the last years. During decaffeination, aroma precursors and bioactive compounds may be extracted. In the present study we evaluate the changes in the chemical composition of C. arabica and C. canephora produced by decaffeination using dichloromethane. A significant change in the chemical composition of both C. arabica and C. canephora species was observed, with differences between species and degrees of roasting. Major changes were observed in sucrose, protein and trigonelline contents after decaffeination. Changes in the levels of total chlorogenic acids and in their isomers distribution were also observed. Lipids and total carbohydrates were not affected as much. The sensory and biological implications of these changes need to be investigated.
  • Metodologia analítica para determinação de folatos e ácido fólico em alimentos Artigo

    Catharino, Rodrigo Ramos; Godoy, Helena Teixeira; Lima-Pallone, Juliana Azevedo

    Resumo em Inglês:

    The aim of this work was to develop and to validate a methodology using HPLC for the simultaneous determination of folates and folic acid in foods. The limits of detection and the recovery rates for the vitamins in the certified reference materials were respectively 5 pg/mL and 94-108% for 5-MTHF, 7 pg/mL and 97-102% for THF, 30 pg/mL and 97.9-104% for 5-FTHF, 30 pg/mL and 95-107 for 10-FFA, 5 ng/mL and 97-102% for FA and 5 ng/mL and 98-103% for 10-MFA. Repeatability showed a coefficient of variation below 3.9% for all the vitamins. The proposed methodology was shown to be efficient when applied to different certified reference materials, namely pig's liver (BCR487), powdered milk (BCR421) and a vegetable mixture (BCR485).
  • Estrutura e propriedades da difenil-4-amina sulfonato de sódio: um dopante de filmes condutores Artigo

    Pires, José Maria; Jorge, Francisco Elias; Machado, Luiz Carlos; Marins, Antonio Augusto Lopes

    Resumo em Inglês:

    This work contains the theoretical simulation of the conformation of diphenyl-4-amine sodium sulphonate (DASNa) and correlates its geometry with conductivity, showing that the conductivity increases as the molecule becomes more planar. The solvent effect was also evaluated, using water and dimethylsulfoxide. Some properties, such as bond distance, vibration al frequency and effective charge were calculated. The utilization of diphenyl-4-amine sodium sulphonate (DASNa) as dopant of aniline was investigated in view of the HOMO-LUMO energy gap.
  • Avaliação dos tratamentos eletroquímico e fotoeletroquímico na degradação de corantes têxteis Artigo

    Catanho, Marciana; Malpass, Geoffroy Roger Pointer; Motheo, Artur de Jesus

    Resumo em Inglês:

    This paper presents the study of the oxidation of three textile dyes (Remazol black B, Remazol Brilliant Orange 3R and Remazol Golden Yellow RNL) using electrochemical and photoelectrochemical methods. In both methods, electrolysis experiments were performed at a current density of 50 mA cm-2 in an aqueous solution of each dye (30 mg L-1), using a photoelectrochemical flow-cell. For all the dyes studied, the photoelectrochemical method was demonstrated to be more efficient than the electrochemical one. Photoelectrochemical oxidation resulted in complete decoloration after 90 min of electrolysis and total organic carbon (TOC) removal reached up to 36%. It was observed that the dyes presenting chromophores at higher wavelengths are removed the quickest, which indicates that photosensitised (photoassisted) oxidation occurs. The level of color was reduced to levels below the standards presented in the literature, which indicates the viability of the photoelectrochemical process as part of the treatment of textile effluents.
  • Nanoparticle-coated organic-inorganic microparticles: experimental design and gastrointestinal tolerance evaluation

    Beck, Ruy Carlos R.; Haas, Sandra Elisa; Guterres, Silvia Stanisçuaski; Ré, Maria Inês; Benvenutti, Edilson V.; Pohlmann, Adriana Raffin

    Resumo em Inglês:

    The influences of the spray-drying parameters and the type of nanoparticles (nanocapsules or nanospheres) on the characteristics of nanoparticle-coated diclofenac-loaded microparticles were investigated by using a factorial design 3². Gastrointestinal tolerance following oral administration in rats was evaluated. Formulations were selected considering the best yields, the best encapsulation efficiencies and the lowest water contents, presenting surfaces completely coated by nanostructures and a decrease in the surface areas in relation to the uncoated core. In vitro drug release demonstrated the influence of the nanoparticle-coating on the dissolution profiles of diclofenac. Nanocapsule-coated microparticles presented a protective effect on the gastrointestinal mucosa.
  • The stability of right- and left-handed alpha-helices as a function of monomer chirality

    Lins, Roberto Dias; Ferreira, Ricardo

    Resumo em Inglês:

    Poly-L-alanine forms stable right-handed alpha-helices, whereas Poly-D-alanine is stable as left-handed alpha helices.
  • Óleo essencial de Gochnatia polymorpha (Less) Cabr. ssp floccosa Cabr. Artigo

    Stefanello, Maria Élida Alves; Cervi, Armando Carlos; Wisniewski Júnior, Alberto; Simionatto, Edésio Luiz

    Resumo em Inglês:

    The essential oil isolated by hydrodistillation from flowers and root bark of Gochnatia polymorpha (Less) Cabr. ssp floccosa Cabr. (Asteraceae) was analyzed by capillary GC/MS. Thirty components were identified in oil of flowers. The composition depends on the stage of flowering. At the beginning of flowering, the main components were (E)-nerolidol (20,4%) and eugenol (17,9%) whereas at the end they were phenylacetaldehyde (14,6%) and tricosane (12,0%). In the essential oil of root bark ten sesquiterpenes were identified. The major components were beta-bisabolene (31,0%) and beta-bisabolol (21,5%). This paper describes for the first time the composition of essential oil in the genus Gochnatia.
  • Metil coenzima M redutase (MCR) e o fator 430 (F430) Revisão

    Nakagaki, Shirley; Friedermann, Geraldo Roberto; Caiut, José Maurício Almeida

    Resumo em Inglês:

    This review presents studies on methyl coenzyme M reductase, the biological system Factor 430 (F430) and the use of nickel(II) complexes as structural and functional models. The ability of F430 and nickel(II) macrocycle complexes to mediate the reductive dehalogenation of cyclohexyl halogens and the CH3-S bond cleavage of methyl CoM (by sodium borohydride and some intermediate species) proposed for the catalytic cycle of the biological system F430 was reviewed. The importance of the structure of the nickel complexes and the condition of the catalytic reduction reaction are also discussed.
  • Alilação e crotilação catalítica e enantiosseletiva de aldeídos Revisão

    Fátima, Ângelo de; Robello, Luís Gustavo; Pilli, Ronaldo Aloise

    Resumo em Inglês:

    The field of chiral catalysis has experienced explosive growth over the last two decades. By now, many of the classical reactions in organic synthesis can be carried out efficiently in asymmetric manner. As one of the fundamental and powerful C-C bond-forming reactions, enantioselective catalytic allylation (ECA) and crotylation (ECC) of aldehydes has attracted considerable attention. In this article, we present an overview about the importance of chiral Lewis acids and bases in catalytic enantioselective addition of allyl- and crotyl metals to aldehydes and the application of this methodology in the total synthesis of natural and non-natural products.
  • Cromatografia em leito móvel simulado na produção de substâncias enantiomericamente puras ou enriquecidas em larga escala Revisão

    Silva Junior, Ivanildo José da; Veredas, Vinícius de; Santos, Marco Antônio Garcia dos; Santana, Cesar Costapinto; Carpes, Marcos José Souza; Correia, Carlos Roque Duarte

    Resumo em Inglês:

    There is great interest nowadays in the use of preparative liquid chromatography as an effective tool for the production of enantiomerically pure, or enriched, compounds for the pharmaceutical industry. To make the chromatographic process economically attractive, attention is now focused on the choice of the chromatographic operating mode to minimize eluent consumption and to maximize productivity. Among the alternatives to the traditional batch chromatography, attention is now shifting towards simulated moving bed (SMB) technologies and a review covering the latest developments in this area seems timely. Several aspects of this important analytical technique are presented and details concerning the SMB technology for process optimization are outlined.
  • Alquilbenzeno sulfonato linear: uma abordagem ambiental e analítica Revisão

    Penteado, José Carlos P.; El Seoud, Omar A.; Carvalho, Lilian R. F.

    Resumo em Inglês:

    The environmental impact of detergents and other consumer products is behind the continued interest in the chemistry of the surfactants used. Of these, linear alkylbenzene sulfonates (LASs) are most widely employed in detergent formulations. The precursors to LASs are linear alkylbenzenes (LABs). There is also interest in the chemistry of these hydrocarbons, because they are usually present in commercial LASs (due to incomplete sulfonation), or form as one of their degradation products. Additionally, they may be employed as molecular tracers of domestic waste in the aquatic environment. The following aspects are covered in the present review: The chemistry of surfactants, in particular LAS; environmental impact of the production of LAS; environmental and toxicological effects of LAS; mechanisms of removal of LAS in the environment, and methods for monitoring LAS and LAB, the latter in domestic wastes. Classical and novel analytical methods employed for the determination of LAS and LAB are discussed in detail, and a brief comment on detergents in Brazil is given.
  • Alcalóides pirrolizidínicos em espécies do gênero Senecio Revisão

    Silva, Chana de Medeiros da; Bolzan, Aline Abati; Heinzmann, Berta Maria

    Resumo em Inglês:

    Senecio species contain a large variety of secondary metabolites and many of these plants afford pyrrolizidine alkaloids. This paper is a review of the literature, describing 62 pyrrolizidine alkaloids already isolated in 62 of more than 2000 species of Senecio, distributed worldwide. The structure-activity relationships involving their toxicity are also discussed, since some Senecio species used for medicinal purposes are responsible for causing serious adverse effects.
  • Aplicações de nanoeletrodos como sensores na Química Analítica Revisão

    Pereira, Francisco Claudece; Bergamo, Erwing Paiva; Zanoni, Maria Valnice Boldrin; Moretto, Ligia Maria; Ugo, Paolo

    Resumo em Inglês:

    Nanomaterials make up an emerging area in Chemistry and in the science of materials. This area constitutes the development of methods for synthesizing nanoscopic particles of a given material used for scientific investigation. Nanomaterials have a wide range of commercial possibilities and technological applications, including their use in analytical chemistry, as well as in electronics, optics, engineering, medicine, devices for liberation of drugs, bioencapsulation, among others. This paper presents a summary about nanoelectrodes, devices built from nanoparticles, which show great potential as electrochemical tools in many different types of analysis. The purpose of this paper is to review the construction methodologies of nanoelectrodes, and to point out their successful applicability in the various fields of immune assays and other analytical procedures with quantitative purposes.
  • N-halossacarinas: reagentes úteis (e alternativos) em síntese orgânica Divulgação

    Souza, Soraia P. L. de; Silva, Joaquim F. M. da; Mattos, Marcio C. S. de

    Resumo em Inglês:

    N-halosaccharins proved to be useful and alternative reagents for diverse organic transformations, such as halogenation of aromatic compounds, benzylic and alpha-carbonylic positions, cohalogenation of alkenes, oxidation of secondary alcohols, etc. Their preparation from saccharin, a cheap and readly available starting material, is simple.
  • Química Analítica de Processos Divulgação

    Trevisan, Marcello G.; Poppi, Ronei J.

    Resumo em Inglês:

    Process Analytical Chemistry (PAC) is an important and growing area in analytical chemistry, that has received little attention in academic centers devoted to the gathering of knowledge and to optimization of chemical processes. PAC is an area devoted to optimization and knowledge acquisition of chemical processes, to reducing costs and wastes and to making an important contribution to sustainable development. The main aim of this review is to present to the Brazilian community the development and state of the art of PAC, discussing concepts, analytical techniques currently employed in the industry and some applications.
  • Polarizabilidade atômica efetiva alfad pode ditar a ionização de radioligantes 99Tc m - diaminoditiol alquilamínicos? Divulgação

    Gonçalves, Marcos Moisés; Fraceto, Leonardo Fernandes; Vila, Marta Maria Duarte Carvalho; Oliveira, Robson Vicente Machado de

    Resumo em Inglês:

    Polarizability correlates well with organic ion stabilization in solution and can be defined as a measure of the relative ease of the distortion of the electronic cloud of a dipolar system exposed to an external electric field. The effective atomic polarizability, alphad, has a fundamental influence on chemical reactivity in the gas phase and in solution. In terms of chemical reactivity the charge is generated within the molecule as a positive charge due to protonation, ionization or resulting from the attack of a nucleophilic anion. In this paper, lipoidal diaminedithiol (DADT) perfusion radioligands based on 99Tc m and possessing an alkylamine side chain have been used to check the influence of alphad on their brain uptake. Some new DADT derivatives, respectively DADT-DIPA (diaminedithiol - diisopropylamine), DADT DIBA (diaminedithiol diisobutylamine), DADT-PR (diaminedithiol - branched pyperidine), have been designed to have high nitrogen alkylamine alphad values. In spite of the fact of higher alphad values having been correlated to higher brain uptakes, there isn't a clear mechanism able to trap these radioligands into the brain space.
  • Princípio e utilização da técnica de efeito miragem de concentração Divulgação

    Trigueiro, João Paulo Campos; Matencio, Tulio; Moraga, Gastón Alvial; Lopez, Christian

    Resumo em Inglês:

    The aim of this work is to present the theoretical and experimental aspects of the mirage effect technique. We are especially interested in the concentration mirage effect, which is a powerful tool in the study of electrochemical reactions that produce ionic movements close to electrodes and to get some fundamental information on mass transport and charge transfer during electrochemical processes. Limitations of this technique are discussed as well as the recent attempts to overcome them.
  • Lesões em DNA induzidas pela autoxidação de S(IV) na presença de íons metálicos de transição Divulgação

    Moreno, Ruben G. M.; Alipázaga, María V.; Medeiros, Marisa H. G.; Coichev, Nina

    Resumo em Inglês:

    The oxidation of sulfite catalyzed by transition metal ions produces reactive oxysulfur species that can damage plasmid and isolated DNA in vitro. Among the four DNA bases, guanine is the most sensitive to one-electron oxidation promoted by the species formed in the autoxidation of sulfite (HSO5-, HO•, SO3•-, SO4•- and SO5•-) due to its low reduction potential and ability to bind transition metal ions capable to catalyze oxidative processes. Some oxidative DNA lesions are promutagenic and oxidative DNA damage is proposed to play a crucial role in certain human pathologies, including cancer.
  • Recentes avanços e novas perspectivas dos eletrodos íon-seletivos Divulgação

    Torres, Karin Yanet Chumbimuni; Marzal, Percy Calvo; Kubota, Lauro Tatsuo; Bakker, Eric

    Resumo em Inglês:

    This paper describes the recent progress in the development of polymeric membranes for ion-selective electrodes. The importance of knowing the mechanism of potential development in membranes for ion-selective electrodes to reach lower detection limits and improve selectivity are discussed. Recent advances and future trends of research on ion-selective electrodes are also reported.
  • Um aparato para monitorar reações rápidas: um "stopped-flow" artesanal de baixo custo Nota Técnica

    Batistela, Vagner Roberto; Tessaro, André Luiz; Soares, Rafael R. da S.; Souza, Vagner Roberto de; Hioka, Noboru

    Resumo em Inglês:

    The modern stopped-flow reaction analyzer has shown high efficiency and flexibility, which provides outstanding sample economy with a dead-time of less than 1 ms. However the cost of the equipment imposes a serious restriction to many Brazilian scientists and teachers. In this work we describe the construction of a low-cost stopped-flow system coupled to a UV-Vis spectrophotometer. The performance of the system was checked by monitoring the kinetics of two reactions: the fading of phenolphthalein in aqueous alkaline solution and the chlorophyll a demetallation in acid medium. The apparatus showed reasonable efficiency with a dead-time of 0.3 to 0.5 s. The very good results obtained in these two illustrative processes show that the system is satisfactory for determining rate constants with mean reaction times ranging from seconds to minutes.
  • On the application of knoevenagel condensation for the synthesis of benzylidene benzothiazine compounds and structural study

    Souza, Ana Maria Alves de; Guarda, Vera Lucia de Miranda; Leite, Lúcia Fernanda Cavalcanti da Costa; Barbosa Filho, José Maria; Lima, Maria do Carmo Alves de; Galdino, Suely Lins; Pitta, Ivan da Rocha

    Resumo em Inglês:

    The synthesis and physico-chemical properties of new 6-acetylamino or 6-benzoyl-amino 2-benzylidene-4-methyl-4H-benzo[1,4]thiazin-3-ones and 6-benzoylamino or 6-nitro 2-benzylidene-4H-benzo[1,4]thiazin-3-ones are described. These benzylidene benzothiazine compounds were prepared by the Knoevenagel condensation with benzaldehydes. The configurations and conformations of benzylidene benzothiazine derivatives were optimised using the semi-empirical method AM1.
  • Determinação dos teores de cobre e grau alcoólico em aguardentes de cana produzidas no estado de Minas Gerais Nota Técnica

    Labanca, Renata Adriana; Glória, Maria Beatriz Abreu; Gouveia, Vitor José Pinto; Afonso, Robson José de Cássia Franco

    Resumo em Inglês:

    The objective of this work was to investigate if producers of sugar cane spirits in Minas Gerais, Brazil, have improved the copper content of their products and also if they have adjusted to the new standards of identity for 'cachaça' and 'aguardente'. Seventy-one samples, obtained from May 2003 until March 2004, were analyzed. Mean copper content was 2.30 mg/L, which indicates a significant reduction in levels. The mean alcohol content was 45.6 % v/v. All of the 'aguardente' but only 79% of the 'cachaça' attended to the standard of identity for alcohol content for these products.
  • Determinação de nitrito em águas utilizando extrato de flores Educação

    Ramos, Luiz Antônio; Cavalheiro, Carla Cristina Schmitt; Cavalheiro, Éder Tadeu Gomes

    Resumo em Inglês:

    Aspects of visible spectrophotometry can be presented to students using simple experiments in which the color of the crude extract of Macroptilium lathyroides (L.) Urb. is bleached in the presence of nitrite ions in acidic medium. The dependence of the absorption intensity with time, the reaction completeness and the Beer law can be demonstrated. Quantitative results for mineral water samples "contaminated" with nitrite ions were obtained from a method based on the Griess reaction and a procedure based on the bleaching reaction between the crude extract and NO2- ions. Both the Griess and the bleaching reactions were found to be time dependent. Recoveries of about 100 - 104% were obtained with these procedures. The use of natural dyes attracted students' interest enhancing the teaching process. Experiments performed by the teaching staff suggested that the proposed methodology can be performed in a 4 h class, with relative errors ranging from 0.19 to 1.86% in relation to the Griess method.
  • Uso de artigos científicos em uma disciplina de Físico-Química Educação

    Santos, Gelson Ribeiro dos; Sá, Luciana Passos; Queiroz, Salete Linhares

    Resumo em Inglês:

    This paper describes the use of primary chemistry literature in a fifth-semester physical chemistry course for undergraduate chemistry students. The main goal is to expose students to the primary literature of physical chemistry, demonstrating how they can benefit from using it. The assignment addresses issues in chemical education such as scientific writing, relating lecture material to the real world, and conducting literature searches. The student evaluation of this assignment, consisting of two surveys and one focus group, showed its usefulness. The details of the evaluation instruments and their results are provided. Out of 45 students enrolled in the course, 30 (67%) students completed the assignment.
  • Justus Von Liebig, 1803-1873. Parte 1: vida, personalidade, pensamento Assuntos Gerais

    Maar, Juergen Heinrich

    Resumo em Inglês:

    This first of two papers allusive to the 200th birthday of Justus von Liebig (1803-1873) deals with the origins, life, education, ideas and influence of one of the great 19th century chemists. The principal characteristics of his "Giessen model of teaching research in chemistry" are presented, as well as the role played by many of his students in the evolution of chemical research in various countries. Liebig's strong personality, his controversies, his contribution to the chemical scene in Giessen and Munich are presented. Although few, the connections with Latin-American chemistry are focused.
  • O inacreditável emprego de produtos químicos perigosos no passado Assuntos Gerais

    Pimentel, Luiz Cláudio Ferreira; Chaves, Camille Rodrigues; Freire, Layla Alvim Alves; Afonso, Júlio Carlos

    Resumo em Inglês:

    This work describes an overview of the use of chemicals in several commercial applications along the XXth century. The use of chemicals by men was largely empirical for many centuries, since there was no organized chemical and toxicological knowledge. During the XIXth century the chemical industry gained a crucial role in the development of technology, as evidenced by the extraordinary increase of new products and their incorporation into everyday life. Chemistry was considered a science capable of solving any problem, little regard being paid to the consequences of the widespread use of new chemicals. Efficiency was more important than safety and consumer information. From tragedies and the development of knowledge on toxicology men adopted more careful protocols before a new chemical was proposed for use. Modern life could not exist without the large-scale employment of a variety of chemicals but information on their responsible and conscious use is now essential. Products that were once considered the "last word in technology" have eventually proven dangerous to humans and the environment in the short or long time range. Previous knowledge on the toxicological dangers and the properties of a given substance or product before commercialization is necessary for safe handling.
  • Eduardo Neves, nosso eterno mestre Assuntos Gerais

    Gutz, Ivano G. R.

    Resumo em Inglês:

    Eduardo Fausto de Almeida Neves, Professor Emeritus of the Universidade Federal de São Carlos and formerly Full Professor at the Instituto de Química - Universidade de São Paulo (USP), São Paulo, Brazil, was born in November 7, 1933 in Pedra Azul, MG, and deceased in July 2, 2006 in São Carlos, SP. He graduated under supervision of Professor Paschoal Senise, pioneer of Analytical Chemistry at USP, and developed his post-doctoral work at Caltech, USA, with Professor Fred Anson. His brilliant career as teacher, scientist, supervisor and mentor resulted in a prolific science school in Analytical Chemistry, with some sixty PhDs and masters supervised by him, amplified to over four hundred in the 2nd to 4th generations (still growing), spread throughout the country and nucleating new research groups. The contents of a hundred papers reflect Prof. Eduardo's wide range of scientific interests. Passionate inclination for creative intellectual activity, rooted in profound knowledge of all branches of Chemistry, broadminded thinking, sound experimentation, generous scientific cooperation and true friendship - that's why friends, colleagues and students referred to him as "master" or "my guru".
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