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Química Nova, Volume: 29, Issue: 3, Published: 2006
  • Editorial

  • Larvicides and acetylcholinesterase inhibitors from Kalanchoe species Artigo

    Trevisan, Maria Teresa Salles; Bezerra, Maria Zeneide Barbosa; Santiago, Gilvandete Maria Pinheiro; Feitosa, Chistiane Mendes; Verpoorte, Robert; Braz Filho, Raimundo

    Abstract in English:

    Acetylcholine esterase inhibitors are successfully used to treat the symptoms of Alzheimer's disease. Extracts of three Kalanchoe species (K. brasiliensis, K. pinnata and K. gastonis-bornieri) showed acetylcholine esterase inhibitory effects and a toxic effect on Aedes aegypti larvae. Here we describe the bioassay guided fractionation of extracts of the most active extracts (K. brasiliensis) which resulted in the isolation of an active mixture of three flavonoids: 8-methoxyquercetin, 3,7-di-O-rhamnopyranoside and 8-methoxykaempferol-3,7-di-O-rhamnopyranoside. On TLC these flavonoids showed an acetylcholine esterase inhibitory effect.
  • Decolorization and toxicity of municipal waste by horseradish (Cochlearia armoracia)

    Dellamatrice, Priscila Maria; Monteiro, Regina Teresa Rosim

    Abstract in English:

    The Municipal Station of Americana, SP, Brazil, treats a volume of 400 l s-1 of effluent, of domestic and textile origin, and produces about 20 t of sludge per day. The plant horseradish, which contains high amount of peroxidases, was able to decolorize this effluent in 2 h and the solid waste in 2 days, at concentrations of 10 and 50%, respectively. However, there was an increase in the toxicity for the bioassays with Hydra attenuatta, Selenastrum capricornutum and lettuce seeds, indicating formation of more toxic substances. Since horseradish showed the ability to decolorize these residues, it can be used as pre-treatment resulting in a sludge of less complex composition.
  • Biomolecular archaeology: preliminary steps for interpretation of the origin of preserved organic residues in Brazilian pre-colonial potsherds Artigo

    Hansel, Fabrício Augusto; Mireski, Sandro Lucio; Madureira, Luiz Augusto dos Santos; Fossari, Teresa Domitila

    Abstract in English:

    Organic residue analysis of archaeological potsherds is a well-established method for determining the uses of European and North American pottery vessels. In the present work we assess if the organic residues identified in Brazilian potsherd extracts are related to commodity processes (e.g. cooking or surface treatment) or to other non-archaeological sources, using as a model potsherds recovered from the Rio do Meio site (Santa Catarina Island). The potsherd extracts are dominated by saturated fatty acids (Ac16:0, with lower abundances of Ac14:0 and Ac18:0). Our studies provide evidence that the organic residues preserved in the Brazilian archeological potsherds are related to foodstuffs and surface treatment processes of the pottery vessels.
  • Multivariati study of urban soils of Teresina city Artigo

    Moura, Márcio Cleto Soares de; Lopes, Ana Nídia Cunha; Moita, Graziella Ciaramella; Moita Neto, José Machado

    Abstract in English:

    The concentrations of Cu, Pb, Zn, Cr, Ni, Al, Mn and Fe were measured by atomic absorption spectrometry, of 19 topsoil samples collected in the Teresina city urban area to discriminate natural and anthropic contributions and identify possible sources of pollution. The average concentrations of Cu, Zn, Pb and Cr of the urban soils were 6.11, 8.56, 32.12 and 7,17 mg/kg-1, respectively. Statistical analysis techniques, such as principal component analysis (PCA) and hierarchical cluster analysis (HCA), were used to analyze the data. Mn, Ni and Cr levels were interpreted as natural contributions, whereas Pb, Zn and, in part, Cu were accounted for mainly by anthropic activities. High Pb levels were observed in the ancient avenues.
  • Determination of ochratoxin A in coriander (Coriandrum sativum L.) by HPCL/fluorescence detection

    Lino, Celeste Matos; Baeta, Lurdes; Pena, Angelina Simões; Silveira, Irene Noronha

    Abstract in English:

    An analytical study based on extraction with acetonitrile-water, immunoaffinity column cleanup, and HPLC/fluorescence detection for separation and identification of ochratoxin A in coriander was carried out. Validation of the applied methodology was done through accuracy and precision studies. Homogenized samples of coriander were spiked in triplicate with ochratoxin A at 0.5, 1.0, 2.0, and 5.0 µg/kg levels. Recovery values were in the range of 98% for a fortification level at 0.5 µg/kg to 109.1% at 1.0 µg/kg. Application to coriander samples available in Portuguese markes showed no contamination with ochratoxin A.
  • A novel method for fast enrichment and monitoring of hexavalent and trivalent chromium at the ppt level with modified silica MCM-41 and its determination by inductively coupled plasma optical emission spectrometry

    Ganjali, Mohammad Reza; Babaei, Leila Hajiagha; Badiei, Alireza; Saberian, Kamal; Behbahani, Seiedmahmoudreza; Ziarani, Ghodsi Mohammadi; Salavati- Niasari, Masoud

    Abstract in English:

    Chromium(III) at the ng L-1 level was extracted using partially silylated MCM-41 modified by a tetraazamacrocyclic compound (TAMC) and determined by inductively coupled plasma optical emision spectrometry (ICP OES). The extraction time and efficiency, pH and flow rate, type and minimum amount of stripping acid, and break- through volume were investigated. The method's enrichment factor and detection limit are 300 and 45.5 pg mL-1, respectively. The maximum capacity of the 10 mg of modified silylated MCM-41 was found to be 400.5±4.7 µg for Cr(III). The method was applied to the determination of Cr(III) and Cr(VI) in the wastewater of the chromium electroplating industry and in environmental and biological samples (black tea, hot and black pepper).
  • Synthesis of allyloxy-ortho-iodobenzamide derivative from d-glucose and tri-n-butyltin hydride mediated radical cyclization reaction Artigo

    Dias, Danielle Ferreira; Prado, Maria Auxiliadôra Fontes; Pinto, Gleydson Daniel; Alves, Ricardo José; Alves, Rosemeire Brondi; Souza Filho, José Dias de

    Abstract in English:

    Methyl 6-O-allyl-2,3-di-O-benzyl-4-deoxy-4-(2 -iodobenzoylamine)-alpha-D-glucopyranoside was synthesized in nine conventional steps from methyl alpha-D-glucopyranoside. Its Bu3SnH-mediated aryl radical cyclization provided a benzomacrolactam, resulting from 11-endo aryl radical cyclization and the reduced uncyclized product methyl 6-O-allyl-4-benzoylamine-2,3-di-O-benzyl-4-deoxy- alpha-D-glucopyranoside. The structures of the three new products were supported by ¹H and 13C NMR spectroscopy and DEPT, COSY and HMQC experiments.
  • Chemical constituents of Galianthe brasiliensis (Spreng.) E.L.Cabral & Bacigalupo (RUBIACEAE) Artigo

    Moura, Vagner Marques de; Santos, Daniela Pereira dos; Santin, Silvana Maria de Oliveira; Carvalho, João Ernesto de; Foglio, Mary Ann

    Abstract in English:

    This paper describes the chemical constituents isolated from aerial parts of the plant Galianthe brasiliensis. From a methanol extract, the iridoid glycosides asperuloside, deacetylasperuloside, mixture of Z- and E-6-O-p-coumaroylscandoside methyl ester, the triterpene ursolic acid and the steroids stigmasterol, campesterol, beta-sitosterol and 3-O-beta-glycopiranosyl sitosterol were isolated. The structures of the natural products were identified on the basis of spectral data, including 2D NMR experiments. The antiproliferative properties of the crude methanolic extract were investigated against a series of nine human cancer cell lines.
  • Biosynthetic origin of acetic acid using SNIF-NMR Artigo

    Boffo, Elisangela Fabiana; Ferreira, Antonio Gilberto

    Abstract in English:

    The main purpose of this work is to describe the use of the technique Site-Specific Natural Isotopic Fractionation of hydrogen (SNIF-NMR), using ²H and ¹H NMR spectroscopy, to investigate the biosynthetic origin of acetic acid in commercial samples of Brazilian vinegar. This method is based on the deuterium to hydrogen ratio at a specific position (methyl group) of acetic acid obtained by fermentation, through different biosynthetic mechanisms, which result in different isotopic ratios. We measured the isotopic ratio of vinegars obtained through C3, C4, and CAM biosynthetic mechanisms, blends of C3 and C4 (agrins) and synthetic acetic acid.
  • Chemical characterization of pitch in Eucalyptus pulp and paper industry Artigo

    Cruz, Mariluze P.; Barbosa, Luiz C. A.; Maltha, Célia R. A.; Gomide, José L.; Milanez, Augusto F.

    Abstract in English:

    The chemical analysis of the acetone, chloroform, toluene and methanol extracts of a pitch sample was carried out by IR and GC-MS, leading to the identification of sixty nine compounds, including fatty acids, alcohols and hydrocarbons. Analysis of the acetone extractive of a eucalyptus wood used in Brazil for pulp production was also carried out, resulting in identification of fifty nine compounds, including mainly fatty acids, phenolic compounds, beta-sitosterol and other steroids. This analysis showed that pitch formation had a contribution from wood extractives and other sources of contamination. The results obtained and the methodology applied can be used by the pulp industry to develop new methods of pitch control.
  • Composition and antifungal activity of essential oils from Piper aduncum, Piper arboreum and Piper tuberculatum

    Navickiene, Hosana M. Debonsi; Morandim, Andréia de A.; Alécio, Alberto C.; Regasini, Luís O.; Bergamo, Debora Cristina B.; Telascrea, Marcelo; Cavalheiro, Alberto J.; Lopes, Márcia N.; Bolzani, Vanderlan da S.; Furlan, Maysa; Marques, Márcia O. M.; Young, Maria C. M.; Kato, Massuo J.

    Abstract in English:

    The composition of essential oils from leaves, stems and fruits of Piper aduncum, P. arboreum and P. tuberculatum was examined by means of GC-MS and antifungal assay. There was a predominance of monoterpenes in P. aduncum and P. tuberculatum and of sesquiterpenes in P. arboreum. P. aduncum showed the richest essential oil composition, including linalool. The essential oils from fruits of P. aduncum and P. tuberculatum showed the highest antifungal activity with the MIC of 10 µg as determined against Cladosporium cladosporioides and C. sphaerospermum, respectively. This is the first report of the composition of essential oils from P. tuberculatum.
  • Rainwater chemistry and atmospheric deposition at Ilha Grande, RJ Artigo

    Souza, Patricia Alexandre de; Mello, William Zamboni de; Maldonado, Juan; Evangelista, Heitor

    Abstract in English:

    Wet (n = 21) and dry (n = 23) deposition samples were collected from March to September 2002 at the southern coast of Ilha Grande. Rainwater pH varied from 4.3 to 6.3 and ionic concentrations (in µmol L-1) decreased in the order Cl- > Na+ > Mg2+ > SO4(2-) > NO3- ~ NH4+ > K+ ~ H+ > Ca2+. Scavenging of sea-salt aerosols was the major source of Cl-, Na+, Mg2+, and Ca2+. Half of total SO4(2-) was non-sea-salt SO4(2-). Total deposition fluxes of NH4+, NO3-, and non-sea-salt SO4(2-) were respectively 9.3, 17.8, and 16.0 mol ha-1 month-1.
  • Determination of volatile and semi-volatile hydrocarbons in the atmosphere Artigo

    Alves, Célia; Pio, Casimiro; Gomes, Paulo

    Abstract in English:

    This paper focuses: (i) the development of a measurement technique for the determination of atmospheric C2-C6 hydrocarbons with sampling in canisters and analysis by gas chromatography/flame ionisation detector (GC/FID), (ii) the improvement of an existent adsorption-sampling technique with Tenax TA tubes for the determination of C6-C11 hydrocarbons and analysis by GC/FID after thermal desorption and cryogenic concentration, (iii) the identification of compounds present in ambient air by gas chromatography/mass spectrometry (GC/MS) for both canister and Tenax samples, (iv) a program of interlaboratorial comparison for quality control of C2-C11 analyses, and (v) the seasonal characterisation of ambient air C2-C11 hydrocarbons.
  • Kinetic and physico-chemical characterization of cashew (Anacardium occidentale L.) wine Artigo

    Torres Neto, Alberto B.; Silva, Moacir Epifânio da; Silva, Wagner Barros; Swarnakar, Ramdayal; Silva, Flávio Luiz Honorato da

    Abstract in English:

    The production of cashew apple wine has the purpose of minimizing the wastage in the Brazilian cashew production. Knowing that the cashew apple fermentation produces a good cashew wine, a study of alcoholic fermentation kinetics of the cashew apple and the physico-chemical characterization of the product were made. The cashew wine was produced in an stirred batch reactor. The results of the physico-chemical analysis of volatiles, residual sugars, total acidity and pH of cashew wine showed that their concentrations were within the standard limits established by the Brazilian legislation for fruit wines.
  • Chemical study of leaves of Chrysophyllum marginatum (Hook. & Arn.) Radlk (Sapotaceae)

    Silva, Viviane Cândida da; Lopes, Márcia Nasser; Bolzani, Vanderlan da Silva

    Abstract in English:

    The fractionation of the antioxidant ethyl acetate extract obtained from the dried leaves of Chrysophyllum marginatum afforded six substances identified as: alpha-amirin, gallic acid, myricitrin, quercitrin, (-)-epigallocatechin and (-)-epigallocatechin-3-O-gallate. This study contributes to the knowledge of the secondary metabolites produced by one more species of the Brazilian Flora, until now not investigated. Moreover, this study allowed the identification of three substances with antioxidant activity previously detected in this species.
  • Adsortion of dichromate ions on the cellulose/ ZrO2.nH2O composite prepared by the methods of conventional precipitation and homogeneos solution precipitation Artigo

    Mulinari, Daniella Regina; Silva, Gilberto Luís J. P. da; Silva, Maria Lúcia Caetano P. da

    Abstract in English:

    This article describes the preparation and characterization of the cellulose/ hydrated zirconium oxide composites prepared by conventional precipitation (PC) and homogeneous solution precipitation (PSH) methods. The composite obtained by the PC method was prepared by using an ammonia solution as the precipitating agent, while the composite obtained by the PSH method was prepared by using urea as the precipitating agent. The adsorption of dichromate ions on the composites was studied using factorial design 2³. The variables were: initial concentration, agitation time and mass of the composite. The data obtained agree better for the composite obtained by the PC method.
  • The use of chemical modified chitosam with succinic anhydride in the methylene blue adsorption Artigo

    Lima, Ilauro S.; Ribeiro, Emerson S.; Airoldi, Claudio

    Abstract in English:

    The adsorption capacity of alpha-chitosan and its modified form with succinic anhydride was compared with the traditional adsorbent active carbon by using the dye methylene blue, employed in the textile industry. The isotherms for both biopolymers were classified as SSA systems in the Giles model, more specifically in L class and subgroup 3. The dye concentration in the supernatant in the adsorption assay was determined through electronic spectroscopy. By calorimetric titration thermodynamic data of the interaction between methyene blue and the chemically modified chitosan at the solid/liquid interface were obtained. The enthalpy of the dye/chitosan interaction gave 2.47 ± 0.02 kJ mol-1 with an equilibrium constant of 7350 ± 10 and for the carbon/dye interaction this constant gave 5951 ± 8. The spontaneity of these adsorptions are reflected by the free Gibbs energies of -22.1 ± 0.4 and -21.5 ± 0.2 kJ mol-1, respectively, found for these systems. This new adsorbent derived from a natural polysaccharide is as efficient as activated carbon. However 97% of the bonded dye can be eluted by sodium chloride solution, while this same operation elutes only 42% from carbon. Chitosan is efficient in dye removal with the additional advantage of being cheap, non-toxic, biocompatible and biodegradable.
  • Hydrolyzable tannins in Bixa Orellana L. Artigo

    Lima, Ricardo Jorge Cruz; Moreno, Antonio Jeferson de Deus; Castro, Solange Fernanda Loureiro de; Gonçalves, José de Ribamar Santos; Olivera, Antonio Benedito de; Sasaki, José Marcos; Freire, Paulo de Tarso Cavalcante

    Abstract in English:

    The aqueous material found in the fruits of Bixa Orellana L. was collected, dried, and characterized using several experimental techniques, namely phytochemical analysis in order to identify the biologically active constituents, Fourier transform infrared (FT-IR) spectroscopy for vibrational analysis, and X-ray powder diffraction in order to identify the presence of crystalline phases in the sample. The results showed that the aqueous material possesses high concentrations of hydrolyzable tannin. This result justifies the anti-inflammatory activity of this substance reported in other studies.
  • Evaluation of the reactivity of iron sulfides and mining wastes: methodology based on cyclic voltammetry

    Monroy, Roel Cruz y Marcos; González, Ignacio

    Abstract in English:

    The mining industry around the world produces an important amount of wastes, which by their high toxic metal and iron sulfide content present a serious environmental problem. Iron sulfide oxidation under weathering conditions provokes the main environmental problem of the mining industry, the generation of Acid Rock Drainage (ARD). Up to now the prediction methodologies do not allow the study of important factors that influence the generation of ARD, producing in some cases erroneous or uncertain conclusions. This paper shows the utilization of cyclic voltammetry using carbon paste electrodes (CPE-Mineral) as an alternative tool in the study of the oxidation capacity of iron sulfides and mining wastes. This electrochemical technique constitutes a novel methodology to establish and understand the factors involved during generation of ARD. Results of several studies including selected sulfide samples and sulfide mining wastes have been described in order to show the capacity of this methodology as a complementary tool in the prediction of the generation of ARD.
  • Isocyanuric chloride acid and cyanuric chloride: general aspects and applications in organic synthesis Revisão

    Cunha, Anna Claudia; Paixão, Fernanda Menezes da; Souza, Maria Cecília B. V. de; Ferreira, Vitor Francisco

    Abstract in English:

    The aromatic six-membered heterocycles having three nitrogen atoms are denominated triazines. Among these heterocycles, isocyanuric chloride and cyanuric chloride are inexpensive and readily available 1,3,5-triazine derivatives, which have been attracting significant attention of organic chemists due to their different kinds of applications, which vary from pharmaceuticals to explosives. This short overview explores their uses in synthetic methods, as chlorinating and oxidating agents and some procedures for their preparation.
  • Use of Blue Rayon for the extraction/concentration of polycyclic compounds in the aquatic environment Revisão

    Kummrow, Fábio; Umbuzeiro, Gisela de Aragão

    Abstract in English:

    This is a review about the use of Blue rayon in the extraction and concentration of environmental contaminants in the aquatic environment. Blue rayon is an adsorbent composed of fibers covalently linked with copper phthalocyanine trisulphonate that has the ability to selectively adsorb polycyclic compounds. Blue rayon can be used in situ, in columns or in flasks. This method showed to be efficient in the extraction of important classes of environmental contaminants like the polycyclic aromatic hydrocarbons (PAHs), aromatic amines and phenylbenzotriazoles (PBTAs) and can be an important tool in monitoring studies for the evaluation of water quality.
  • Continuum solvation models: fundamentals Revisão

    Pliego Jr, Josefredo R.

    Abstract in English:

    Continuum solvation models are nowadays widely used in the modeling of solvent effects and the range of applications goes from the calculation of partition coefficients to chemical reactions in solution. The present work presents a detailed explanation of the physical foundations of continuum models. We discuss the polarization of a dielectric and its representation through the volume and surface polarization charges. The Poisson equation for a dielectric was obtained and we have also derived and discuss the apparent surface charge method and its application for free energy of solvation calculations.
  • Effects of the solvent composition on the stability of proteins in aqueous solutions Revisão

    Fonseca, Lúbia Cristina; Corrêa, Natássia Caroline Resende; Garrote-Filho, Mario da Silva; Cunha, Cleine Chagas da; Penha-Silva, Nilson

    Abstract in English:

    A protein presents a native (N) macro state, which is functionally active, in equilibrium with the denatured (D) macro state, which is devoid of biological activity. An ensemble of microstates forms each macrostate. The denatured state comprises a greater ensemble of microstates than the native macrostate. The N-D equilibrium can be affected by several factors, that comprise the purity of the water, temperature, pH and solute concentration. This work discusses the influence of osmolytes and chaotropics on the N-D equilibrium in aqueous solutions.
  • Calophyllum genus: chemical and pharmacological importance Divulgação

    Noldin, Vânia Floriani; Isaias, Daniela Buffon; Cechinel Filho, Valdir

    Abstract in English:

    The Calophyllum genus (Clusiaceae) is composed of about 200 species, with a pantropical distribution. Some species are medicinal and are used against several diseases, including gastric ulcers, infectious pathologies, painful, inflammatory processes and as molluscicidal. A search in the literature regarding the chemical and biological aspects of these plants indicates cytotoxic activity against several cell lines, inhibition of HIV-1 reverse transcriptase, antisecretory and cytoprotective properties, antinociceptive, molluscicidal and antimicrobial effects, among others, related particularly to the presence of coumarins, xanthones, flavonoids, and triterpenes.
  • HIV-integrase inhibitors: potential pharmacological approach for AIDS therapy Divulgação

    Melo, Eduardo Borges de; Bruni, Aline Thaís; Ferreira, Márcia Miguel Castro

    Abstract in English:

    AIDS has the HIV as its etiological agent. Researches has been done to find new pharmacological agents to be used in therapy, because of problems of resistance and side effects. The HIV-integrase inhibitors are some of those new agents that are being studied. This updating focusses on the fundamental information about HIV and HIV-integrase and the main methods being used to develop these new drugs, with examples for each case.
  • Singlet oxygen-mediated protein oxidation: damage mechanisms, detection techniques and biological implication Divulgação

    Ronsein, Graziella E.; Miyamoto, Sayuri; Bechara, Etelvino; Di Mascio, Paolo; Martinez, Glaucia R.

    Abstract in English:

    Proteins are potential targets for singlet molecular oxygen (¹O2) oxidation. Damages occur only at tryptophan, tyrosine, histidine, methionine, and cysteine residues at physiological pH, generating oxidized compounds such as hydroperoxides. Therefore, it is important to understand the mechanisms by which ¹O2, hydroperoxides and other oxidized products can trigger further damage. The improvement and development of new tools, such as clean sources of ¹O2 and isotopic labeling approaches in association with HPLC/mass spectrometry detection will allow one to elucidate mechanistic features involving ¹O2-mediated protein oxidation.
  • 1,2,3-triazolic heterocycles: history, preparations, applications and pharmacological activities Divulgação

    Melo, Júlio O. F.; Donnici, Claudio Luis; Augusti, Rodinei; Ferreira, Vitor F.; Souza, Maria Cecília B. V. de; Ferreira, Maria Lourdes G.; Cunha, Anna C.

    Abstract in English:

    The 1,2,3-triazole, known since the end of 19th century, is a very widely used heterocyclic system present in many synthetic substances and commercial pharmaceutical compounds. In fact, 1,2,3-triazoles show several applications in many areas especially as medicines against many diseases like cancer, AIDS, Parkinson and Alzheimer. Nowadays there is a large variety of known methods to obtain these heterocyclic compounds comprising mainly three synthetic routes. Nevertheless, there is no article that gives an objective overview of the synthetic methods for obtaining these kinds of azoheterocycles. This paper presents a brief history of this class of compounds, and a synthetic discussion concerning the main synthetic methods for its preparation, such as cyclization through hydrazones, concerted cycloadditon [2+3] and pseudopericyclic cyclization - and some others of restricted application, but also important. Finally, this paper also provides a brief overview on pharmacological applications of some 1,2,3-triazoles.
  • Development of a device to valuate the effect of ethanol on the vapor pressure and vaporization enthalpy of fuel gasolines Nota Técnica

    Cataluña, Renato; Silva, Rosângela

    Abstract in English:

    The quality of the gasoline utilized for fueling internal combustion engines with spark ignition is directly affected by the gasoline's properties. Thus, the fuel's properties must be in perfect equilibrium to allow the engine to perform optimally, not only insofar as fuel consumption is concerned, but also in order to reduce the emission of pollutants. Vapor pressure and vaporization enthalpy are important properties of a gasoline determining the fuel's behavior under different operating conditions in internal combustion engines. The study reported here involved the development of a device to determine the vapor pressure and the vaporization enthalpy of formulations containing volumes of 5, 15 and 25% of ethanol in four base gasolines (G1, G2, G3 and G4). The chemical composition of these gasolines was determined using a gas chromatographer equipped with a flame ionization detector (FID).
  • Determination of chloramphenicol residues in industrialized milk and honey samples using LC-MS/MS Nota Técnica

    Martins Júnior, Helio Alves; Bustillos, Oscar Vega; Pires, Maria Aparecida Faustino; Lebre, Daniel Temponi; Wang, Alexandre Yautin

    Abstract in English:

    The present work shows a method for the determination of chloramphenicol (CAP) antibiotic in milk, powder milk and honey. The solid phase extraction and liquid-liquid extraction were applied as a clean-up and pre-concentration strategies followed by LC-ESI/MS/MS analysis. The recovery was studied for different fortification levels from 0.05 to 1.00 µg L-1 in milk, showing values between 91 101% and RSD bellow 8.0%, while honey was spiked with a concentration of 0.20 µg kg-1 yelding a mean recovery of 83% and RSD of 6.5%. The quantification transition 321>152 showed a LOD of 0.52 ng kg-1 and LOQ of 1.85 ng kg-1.
  • Potentiometric titration applied to free fatty acid determination of edible oils and fats Nota Técnica

    Osawa, Cibele Cristina; Gonçalves, Lireny Ap. Guaraldo; Ragazzi, Sidnei

    Abstract in English:

    Free fatty acids are a measure of evaluating fats and oils, submitted to abusive conditions, besides being a quality characteristic of edible vegetable oils. The official method of determination (AOCS Ca 5a-40, 2004) is based on titration, using phenolphthalein as an indicator. For crude and degummed oils, the titration end point is difficult to be observed due to the high level of pigments, resulting in dark solutions. In this case and others, such as self-life studies, in which sample quantities are limited, potentiometric titration may be a very good alternative.
  • The pKa of acid-base indicators and the influence of colloidal systems Educação

    Previdello, Bruno Alarcon Fernandes; Carvalho, Fernando Rodrigues de; Tessaro, André Luiz; Souza, Vagner Roberto de; Hioka, Noboru

    Abstract in English:

    An experiment is proposed that can be included in undergraduate courses of chemistry. The subject is the acidity of organic compounds, which are employed as pH indicators, particularly in acid-base titrations. The indicators used are methyl orange, bromophenol blue and bromocresol green in aqueous medium. The influence of colloidal systems on the equilibrium is evaluated by the pKa. The colloids employed are surfactants like sodium dodecyl sulfate, cetyl-trimethylammonium bromide and a polymeric non-ionic F127 (pluronics). The effect of stabilization promoted by the system on the acidic or basic structureof the indicator establishes the action mechanism of the colloid on the pKa values.
  • Study of the photochromic behaviour of a naphthopyran: a simple experiment illustrative of the photochromic phenomenon Educação

    Coelho, Paulo J.

    Abstract in English:

    An easy experiment on the synthesis of 3,3-diphenyl-3H-naphtho[2,1-b]pyran and characterization of its photochromic behaviour is reported. Upon irradiation of an uncoloured toluene solution of 3,3-diphenyl-3H-naphtho[2,1-b]pyran with near UV light, an intense yellow colouration is produced due to the formation of two coloured open forms. When the irradiation source is removed the coloured open forms return to the uncoloured state. The analysis of the absorbance decay with time allows the determination of the discoloration rate constants of each open form. The reversibility of the photochromic phenomenon, well demonstrated by the exposure of the solution to sunlight for a few seconds, is particularly attractive to the students.
  • Chemistry literacy, planetary education and social inclusion Educação

    Santos, Wildson Luiz Pereira dos

    Abstract in English:

    From the different conceptions on scientific and technology literacy (STL), and reflections on globalization and social inclusion, this paper points out the responsibility of the chemists in social actions by their associations for supporting political actions to improving the quality of life, and to protecting the environment by sustainable development for changing the modern society. Supporting ideas for equity within the society between the nations, and giving examples from approaching of socioscientific issues of the textbook "Chemistry and Society", it demonstrated the role of the teachers and the chemistry professionals to realize the STL of the people in the planetary perspective.
  • "Façamos Químicos" [Let's Make Chemists]: the "birth certificate" of chemistry undergraduate courses in Brazil Assuntos Gerais

    Santos, Nadja Paraense dos; Pinto, Ângelo C.; Alencastro, Ricardo Bicca de

    Abstract in English:

    This work presents a brief retrospective of José de Freitas Machado's prominent role in the creation, development and consolidation of Chemistry undergraduate courses in Brazil. Freitas Machado defended in many occasions the importance of chemical studies for the economic development of this country. We analyze, here, his important paper "Façamos Químicos" [Let's Make Chemists] (1917), seminal for the implantation of Industrial Chemistry undergraduate courses in Brazil.
  • A importância da Química Analítica Qualitativa nos cursos de Química das instituições de ensino superior brasileiras Carta Ao Editor

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