Showing papers in "Journal of the Brazilian Chemical Society in 2011"

Recent advances in 1,4-benzoquinone chemistry

Abstract: 1,4-Benzoquinones are ubiquitous in nature and can be synthesized by diverse strategies. Recent developments on their synthetic methodologies, cycloaddition reactions, computational chemistry and pulse radiolytic studies are reported in this review. Their chemical and biological significance as well as their derivates' are also covered.

Dry washing in biodiesel purification: a comparative study of adsorbents

Abstract: The purpose of this work is to compare the efficiency of different adsorbents in the purification of biodiesel produced by alkaline transesterification of soybean oil (Methanol/KOH). The proposed methodologies were based on the use of Magnesol®, silica, Amberlite BD10 DRY® and Purolite PD 206® as adsorbents and were developed by adsorption at 65 oC. The response of each adsorbent was measured through the residual potassium, alcohol, water and soaps dissolved in the purified biodiesel. As a result, we observe that Magnesol® and silica showed better adsorption properties than Amberlite BD10 DRY® and Purolite PD 206®, especially for removing soap, free and bonded glycerol and potassium. In comparison to the conventional acid water washing, these matrices were found to be equally appropriate for the removal of inorganic and organic contaminant species from biodiesel. The main results found for these two adsorbents (Magnesol® 1% and silica 2%) were values below 0.17 mg KOH g-1 for acid number, 1 mg kg-1 of K, 61 ppm of soap, 500 mg kg-1 of water, 0.22% of methanol and 0.03% of free glycerol

Spatial and seasonal variations of pharmaceuticals and endocrine disruptors in the Atibaia River, São Paulo State (Brazil)

Abstract: A single run optimization chromatographic method for the determination of 15 emerging contaminants in surface water was optimized using solid-phase extraction (SPE) and high performance liquid chromatography (HPLC) with detection through ultraviolet-diode array (UV-DAD) or fluorescence (FLD). Selected compounds included acetaminophen, acetylsalicylic acid, diclofenac, ibuprofen, caffeine, 17β-estradiol, estrone, progesterone, 17α-ethynylestradiol, levonorgestrel, diethylphthalate, dibutylphthalate, 4-octylphenol, 4-nonylphenol and bisphenol A. Quality parameters of the proposed method showed a linearity r2 > 0.996, coefficient of variation lower than 5%, recoveries between 80 to 120% for a spike of 10 µg L-1 for each of the 15 compounds. The lowest limit of detection (LOD) was 38 ng L-1 for caffeine, whereas the highest value was 170 ng L-1 for ibuprofen. The method was applied to the spatial and seasonal monitoring of these compounds in the Atibaia River, which is the main drinking water source for Campinas City (Sao Paulo State, Brazil). Among the 15 selected emerging contaminants, 10 were detected at least once. The lowest concentration determined was 0.096 µg L-1 for diclofenac, whereas caffeine showed concentrations as high as 127 µg L-1.

Biosensors based on gold nanostructures

Abstract: The present review discusses the latest advances in biosensor technology achieved by the assembly of biomolecules associated with gold nanoparticles in analytical devices. This review is divided in sections according to the biomolecule employed in the biosensor development: (i) immunocompounds; (ii) DNA/RNA and functional DNA/RNA; and (iii) enzymes and Heme proteins. In order to facilitate the comprehension each section was subdivided according to the transduction mode. Gold nanoparticles based immunosensors have a wide range of applications in food, environmental, pharmaceutical, chemistry and clinical diagnostics. The nanoparticles were employed to improve whether the analytical signal or the immunocompounds immobilization. In another section, biosensors based on DNA/RNA biomolecules employing gold nanostructures as labels and label-free funtional DNA/RNA biosensors associated to gold nanostructures as tranducers were systematically reported for rapid identification of pathogens, species of environmental interest and clinical diagnostics, respectively. The inclusion of gold nanoparticles in modified electrodes itself enhances the electron transfer between the transducer and biomolecules leading to improved bioanalytical devices when redox enzymes and heme proteins are used. Biosensors for the detection and quantification of glucose and hydrogen peroxide are discussed as well.

Antioxidant activity and composition of propolis obtained by different methods of extraction

Abstract: Ethanolic extracts of propolis obtained with different concentrations of propolis and made using hydrous ethanol with various water/ethanol contents were analyzed. The antioxidant action of the extracts was determined by free radical 1,1-diphenyl-2-picryl-hydrazyl (DPPH·) scavenging and by ferric reducing ability power (FRAP), using the ferric-tripyridyl triazine (Fe3+-TPTZ) complex. The total phenolic and flavonoid contents were also determined, and the electrospray ionization mass spectrometry spectra (ESI(-)-MS) of the extracts were acquired. The chemical composition of propolis extracts and their antioxidant activity were observed to vary with the concentration of propolis, and especially with the water/ethanol contents of the hydrous ethanol used for extraction. The antioxidant activity of the extracts was also found to be significantly dependent on these extraction parameters, as well as on the composition of the phenolic compounds and flavonoids. FRAP values showed, however, poor correlation with the flavonoid content

Citrinin derivatives from the soil filamentous fungus Penicillium sp. H9318

Abstract: Investigation of a microbial fermentation organic extract of Penicillium sp. H9318 led to the isolation of a new isoquinolinone alkaloid, (5S)-3,4,5,7-tetramethyl-5,8-dihydroxyl-6(5H)-isoquinolinone (1), along with four known citrinin derivatives (2-5). Citrinin (2) exhibited significant inhibitory activity against Streptomyces 85E in the hyphae formation inhibition (HFI) assay, while compounds 1, 3-5 were not active when tested at 20 mg/disk in the HFI assay. Citrinin (2) further demonstrated a weak inhibitory activity against MCF-7 (IC50 71.93 µmol L-1), LNCaP (IC50 77.92 µmol L-1), LU-1 (147.85 µmol L-1) and KB (IC50 65.93 µmol L-1) cell lines, respectively, in the cytotoxicity assay.

Chemical and spectroscopic characterization of a vegetable oil used as dielectric coolant in distribution transformers

Abstract: In this work, a complete UV-Vis, IR and (1H, 13C and DEPT) NMR spectroscopic analysis was performed for a FR3® vegetable oil sample used as dielectric coolant in an experimental distribution transformer. The same spectroscopic analysis was performed for three used FR3® oil samples (i.e., 4 months in use, 8 months in use and 7 years in use), removed from several operating distribution transformers. Comparison of the data indicated that no significant spectroscopic changes, and hence, no structural changes occurred to the oils by the use. Chemical transformations like catalytic hydrogenation (hardening) and hydrolysis were performed to the FR3® oil sample and the obtained products were analyzed by spectroscopic methods in order to collect further structural information about the FR3® oil. Accelerated aging tests in laboratory were also performed for three FR3® oil samples affording interesting information about the structure of the degradation products. These findings would be valuable to search for a spectroscopy-based technique for monitoring the life-time and performance of this insulating vegetable oil.

Simple route for the synthesis of copper hydroxy salts

Abstract: The current work introduces a new and rapid synthetic route for the in-laboratory preparation of copper hydroxy nitrate, through the reaction of magnesium hydroxide and copper nitrate aqueous solution. The material with the formula Cu2(OH)3NO3 and monoclinic phase was characterized by X-ray diffraction, atomic absorption, Fourier transform infrared and Raman spectroscopy, scanning electron microscopy with EDX, and thermal analysis.

Extraction of lignin from sugar cane bagasse and its modification into a high performance dispersant for pesticide formulations

Abstract: Com o objetivo de utilizar efetivamente um sub-produto de material nao madeireiro, foi extraida lignina do bagaco de cana-de-acucar via acidificacao do licor negro. A lignina extraida do bagaco da cana-de-acucar (EBL) foi modificada por oxidacao, hidroximetilacao e sulfonacao em um lignossulfonato soluvel em agua (EBL-M). O composto foi caracterizado por IR, UV, GPC e analise elementar. Os resultados mostraram que as unidades aromaticas do EBL-M foram mantidas e efetivamente sulfonadas e que a porcentagem de S foi alta (7,82%). A eficiencia de dispersao de EBL-M para formulacoes pesticidas foi comparada com dispersantes comerciais via medicao da frequencia de suspensao. Como esperado, EBL-M mostrou a mesma eficiencia de outros lignossulfonatos comerciais para dispersar kinsperse, quando usados para grânulos de dimetomorfe dispersiveis em agua. A caracterizacao atraves do peso molecular e do teor de lignossulfonatos no grupo sulfonico, sugeriu que a eficiencia dispersante aumentou com o maior teor de grupo sulfonico e maior peso molecular. Quando usado para grânulos de tribenuron dispersiveis em agua, a eficiencia dispersante de EBL-M foi muito proxima dos dispersantes comerciais. In order to effectively utilize a by-product of non-wood material, lignin was extracted from sugar cane bagasse via acidification of black liquor. The extracted sugar cane bagasse lignin (EBL) was modified by oxidation, hydroxymethylation, and sulfonation into a water-soluble lignosulfonate (EBL-M). It was characterized by IR, UV, GPC and elemental analysis. The results showed that the aromatic units of EBL-M were kept well and it was effectively sulfonated, that the percentage of S was high as 7.82%. The dispersing efficiency of EBL-M for pesticide formulations was compared with commercial dispersants via suspending rate measurement. As expected, EBL-M had the equal optimal dispersing efficiency to kinsperse than other commercial lignosulfonates when being used for dimethomorph water dispersible granules. The characterization of molecular weight and sulfonic group’s content of lignosulfonates suggested that the dispersing efficiency increased with higher sulfonic group’s content and higher molecular weight. As to being used for tribenuron water dispersible granules, the dispersing efficiency of EBL-M was much close to the commercial dispersants.

Enzymatic hydrolysis of cassava starch for production of bioethanol with a colombian wild yeast strain

Abstract: A hidrolise enzimatica do amido de mandioca para producao de xaropes de glucose foi avaliada usando alfa-amilase de Bacillus licheniformis e glucoamilase de Aspergillus niger. Tambem, uma mistura enzimatica composta de α-amylase de Aspergillus kawachi e glucoamilase de Aspergillus niger foi testada. As condicoes da enzima para a hidrolise do amido foram otimizadas por um planejamento fatorial experimental (33×2) usando como variaveis a concentracao do substrato, a relacao enzima/substrato e o tempo de reacao. As condicoes otimas de reacao com 100 g de amido per L foram: α-amilase pH 5,0, 80 °C e 130,5 U g-1 de amido; glucoamilase pH 4,5, 70 °C e 81,5 U g-1 de amido. Adicionalmente, as condicoes otimas da mistura enzimatica foram pH 4,5, 46 °C e 16,4 U g-1 de amido. Finalmente, a producao de alcool usando xaropes de glucose a partir do amido hidrolisado enzimaticamente foi realizada usando uma cepa selvagem de Candida sp isolada do caldo de cana de acucar, obtendo produtividades em etanol volumetrico em torno de 1,8-3,2 g L-1h-1.

Effect of temperature on methylene blue decolorization in aqueous medium in electrical discharge plasma reactor

Abstract: This study investigates the effect of bath solution temperature on methylene blue decolorization in a point-to-plate electrical discharge plasma reactor. The results show an increase in the initial percentage of dye decolorization with an increase in the bath solution temperature from 4 to 28 oC, but from 28 to 37 oC there was no change. However, when the temperature was raised to 47 oC the initial dye decolorization percentage decreased. The hydrogen peroxide (H2O2) formation in water during the plasma treatment decreased as the bath temperature increased from 4 to 47 oC. The dye decolorization reaction occurred via a complex mechanism where zero- and first-order processes took place at the same temperature, following zero-order in the initial step and first-order with the progress of the reaction. The activation energy involved in the first-order process was 13.09 kJ mol-1.

Design of experiments (DOE) for the optimization of hydrothermal synthesis of hydroxyapatite nanoparticles

Abstract: The aim of this work was to investigate the influence of different reaction parameters on the properties of hydroxyapatite (HAp) nanoparticles prepared by the hydrothermal method. The literature data describe widely different experimental conditions for the hydrothermal synthesis of HAp. A specific approach was therefore used to evaluate the statistically influential factors among those described in the literature. The role of each experimental parameter was also discussed within the framework of particle nucleation and crystal growth mechanism. Among the selected variables, temperature and pH were found to be the most significant factors affecting the composition and morphology of the HAp. Moreover, in the present study, different morphologies ranging from rod-like to spherical nanoparticles with various characteristics were successfully obtained, which can be applicable for the preparation of various HAp bioceramics.

Photocatalytic production of hydrogen: an innovative use for biomass derivatives

Abstract: Hydrogen is considered the energy carrier of the future because of its clean and very flexible conversion into different forms of energy, e.g., into heat via combustion or electricity via fuel cells. Traditionally, hydrogen is produced from natural gas steam reforming from fossil fuels making the effective implementation of hydrogen economically and environmentally unsustainable. To overcome this problem, several routes are being proposed for hydrogen production from renewable sources. Recent research points to the photoinduced reforming of biomass as a promising possibility, since it uses solar radiation, an inexhaustible source of energy, and raw materials derived from renewable sources such as biomass and water. Studies in this field are still incipient but quite encouraging. The process combines photocatalytic water splitting with the photodecomposition of organic compounds mediated by an irradiated semiconductor. In this process, the water oxidation reaction is suppressed by a sacrificial electron donor (biomass), as well as the formation of superoxide radicals when the reaction is carried out under anaerobic conditions. The hydrogen production rates from photoinduced reforming are similar or superior to other processes, including biomass hydrolysis and aqueous phase reforming. However, the major researches into hydrogen production by photoinduced reforming of biomass derivatives have focused on TiO2, which limits the portion of solar radiation absorbed as UV light. Thus, the current challenge in this field is the development of narrow band gap semiconductors that are able to drive the photoinduced reform of biomass with visible light, which corresponds to about 43% of solar radiation.

An HPLC-DAD method to quantification of main phenolic compounds from leaves of Cecropia Species

Abstract: An efficient and reproducible HPLC-DAD method was developed and validated for the simultaneous quantification of major compounds (chlorogenic acid, isoorientin, orientin and isovitexin) present in the leaves of two Cecropia species, C. glaziovii and C. pachystachya. From the leaves of C. glaziovii and C. pachystachya were isolated the C-glycosylflavones isoorientin and isovitexin and identified on both species chlorogenic acid (3-O-caffeoylquinic acid) and the O-glycosylflavonol isoquercitrin. The C-glycosylflavone orientin was isolated only from C. pachystachya. Chlorogenic acid was the major compound in both species (11.1 mg g-1 of extract of C. glaziovii and 27.2 mg g-1 of extract of C. pachystachya) and for the flavonoids quantified, isovitexin was the main C-glycosylflavonoid for C. glaziovii (4.6 mg g-1 of extract) and isoorientin the main one for C. pachystachya (17.3 mg g-1 of extract).

One-pot synthesis of 4H-Chromene and Dihydropyrano[3,2-c]chromene derivatives in hydroalcoholic media

Abstract: 4H-Chromenes and dihydropyrano[3,2-c]chromenes are obtained in good to excellent yields by a simple, mild and efficient procedure using poly(N,N'-dibromo-N-ethyl-benzene-1,3-disulfonamide) [PBBS] and N,N,N',N'-tetrabromobenzene-1,3-disulfonamide [TBBDA ] as catalysts

Synthesis of dihydropyrimidin-2-one/thione library and cytotoxic activity against the human U138-MG and Rat C6 glioma cell lines

Abstract: Two series of 4-aryl-3,4-dihydropyrimidin-2(1H)-(thio)ones including monastrol (1a), have been synthesized by an environment-friendly methodology based on the combined use of citric acid or oxalic acid and TEOF (triethylorthoformate). The library was evaluated as inhibitor of cell proliferation on two glioma cell lines (human-U138-MG and Rat-C6). The compounds derived from thiourea 1f and 1d were more cytotoxic than monastrol. The compound derived from urea 2d showed the highest cytotoxic activity among the analyzed compounds.

Synthesis and characterization of brush-like ZnO nanorods using albumen as biotemplate

Abstract: Crystalline ZnO nanorods with wurtzite-like structure and average diameter of 90 nm and length >1 µm, was prepared by calcination (700 oC) of a Zn(II)/albumen hybrid obtained by sol-gel method, by the reaction of Zn(II) acetate and egg white (albumen), in aqueous solution. The material was characterized by powder X-ray diffraction (XRD), scanning electron (SEM) and transmission electron microscopy (TEM), thermogravimetric analysis (TGA/DTA), N2 adsorption/desorption (BET method), FT-IR and photoluminescence (PL) spectroscopy. The surface area was determined to be 6.91 m2 g-1 by BET method. The TGA/DTA thermal events were consistent with the decomposition of albumen at 300 oC and final formation of ZnO at 578.5 oC. The results showed that albumen act as template playing essential role on defining the formation of ZnO nanorods with brush-like morphology.

Molecular dynamics simulations and QM/MM studies of the reactivation by 2-PAM of tabun inhibited human acethylcolinesterase

Abstract: A elucidacao das rotas de reativacao da acetilcolinesterase humana (HuAChE) inibida por organofosforados e de crucial importância para o desenvolvimento de antidotos eficientes contra a intoxicacao causada por agentes de guerra quimica. Com o objetivo de contribuir para uma melhor compreensao do mecanismo de reativacao, foram aplicadas neste trabalho simulacoes de dinâmica molecular (DM) classica para estudar as interacoes entre a pralidoxima e aminoacidos do sitio ativo da HuAChE inibida pelo agente neurotoxico tabun. Alem disso, metodos hibridos de mecânica quântica/mecânica molecular (QM/MM) foram usados para propor um mecanismo de reativacao para a enzima inibida. Os resultados mostraram que a DM classica manteve a pralidoxima no interior do sitio ativo da enzima, em uma regiao favoravel a ocorrencia de uma possivel reacao de desfosforilacao, que foi confirmada por metodos de QM/MM, levando a proposta de um mecanismo de reativacao, energeticamente favoravel. The elucidation of the reactivation routes of human acetylcholinesterase (HuAChE) inhibited by organophosphorous compounds is of crucial importance to the development of efficient antidotes against poisoning by chemical warfare agents. In order to contribute to a better understanding of the reactivation mechanism, we applied, in this work, classical molecular dynamics (MD) simulations to study the interactions between pralidoxime and the active site's amino acids of HuAChE inhibited by the neurotoxic agent tabun. Further, quantum mechanical/molecular mechanical (QM/MM) hybrid methods were used to propose a reactivation mechanism for the inhibited enzyme. The results showed that the classic MD kept pralidoxime inside the enzyme's active site, in a favorable region to the occurrence of possible reactions of dephosphorilation, which were confirmed by QM/MM methods, and lead to the proposition of an energetically favorable mechanism of reactivation.

Distribution of pesticide residues in rice grain and in its coproducts

Abstract: LOQ for the mixture of pesticides and rice and rice bran recoveries of 119 and 116%, 84 and 119%, 113 and 96%, 103 and 97% for carbofuran, bispyribac-sodium, clomazone and tebuconazole, respectively. The method under development was applied to rice fractions: bran had the highest residue concentration of the studied pesticides, when compared to milled rice, showing 8.0, 2.3, 2.2 and 1.6 times more contamination, in average, with tebuconazole, clomazone, carbofuran and bispyribac-sodium, respectively. Only clomazone and tebuconazole were in the acceptable limits established by Codex Alimentarius (0.1 mg kg -1 ) for milled rice.

Elemental Analysis of Wines from South America and their Classification According to Country

Abstract: Elementos majoritarios, minoritarios e traco em vinhos provenientes de paises produtores na America do Sul (Argentina, Brasil, Chile e Uruguai) foram determinados. A espectrometria de emissao optica com plasma indutivamente acoplado (ICP OES) e a espectrometria de massa com plasma indutivamente acoplado (ICP-MS) em conjunto com nebulizacao pneumatica e/ou nebulizacao ultra-sonica foram utilizadas. Foram determinados 45 elementos (Al, Ag, As, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Gd, Ho, K, La, Li, Lu, Mg, Mn, Mo, Na, Nd, Ni, P, Pb, Pr, Rb, Sb, Sn, Se, Sm, Sr, Tb, Ti, Tl, Tm, U, V, Yb e Zn) em 53 vinhos tintos. Mediante analise multivariada, os vinhos puderam ser discriminados de acordo com o pais de origem, independentemente do tipo da uva. Os elementos discriminantes foram Tl, U, Li, Rb e Mg. Major, minor and trace elements in wines from wine-producing countries in South America (Argentina, Brazil, Chile, and Uruguay) were determined. Inductively coupled plasma optical emission spectrometry (ICP OES) and inductively coupled plasma mass spectrometry (ICP-MS) combined with pneumatic and/or ultrasonic nebulization were used. The concentrations of 45 elements (Al, Ag, As, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Gd, Ho, K, La, Li, Lu, Mg, Mn, Mo, Na, Nd, Ni, P, Pb, Pr, Rb, Sb, Sn, Se, Sm, Sr, Tb, Ti, Tl, Tm, U, V, Yb, and Zn) in 53 red wines were determined. By means of multivariate analysis, the wines could be discriminated according to the country of origin, regardless of the type of grape. The discriminant elements were Tl, U, Li, Rb, and Mg.

Metal fractionation in sediments of the Sergipe River, northeast, Brazil

Abstract: The sequential extraction procedure proposed by the European Community Bureau of Reference (BCR) was applied for the fractionation of Cd, Cr, Cu, Ni, Pb and Zn in sediments from the Sergipe Estuary, Brazil. The method showed satisfactory recoveries, detection limits and standard deviations for trace metals determinations in sediment samples. Cd was the metal with the greatest percentage in the exchangeable fraction. Pb and Ni were present mainly in the reducible and oxidizable fractions. Cr, Cu and Zn were predominantly associated with the residual fraction. The order of mobility of metals extracted was Pb > Cd > Ni > Cu > Cr > Zn. According to the risk assessment code (RAC), the sediments showed low to medium risk for all metals.

Electrochemical degradation of the dye reactive orange 16 using electrochemical flow-cell

Abstract: Electrochemical removals of color and organic load from solutions containing the dye reactive orange 16 (RO16) were performed in an electrochemical flow-cell, using a platinum working electrode. The influence of the process variables flow-rate, such as NaCl concentration, applied potential and solution pH, were studied. The best color removal achieved was 93% (λ = 493 nm) after 60 min at 2.2 V vs. RHE electrolysis, using 1.00 g L-1 NaCl as supporting electrolyte. The rises in the concentration of NaCl and applied potential increased the color removal rate. The best total organic carbon removal (57%) was obtained at 1.8 V, without the separating membrane, indicating that the ideal conditions for the color removal are not necessarily the same as those to remove the total organic carbon. The degradation efficiency decreased with the solution pH decrease.

A convenient and efficient protocol for the one pot synthesis of 3,4-Dihydropyrimidin-2-(1H)-ones catalyzed by ionic liquids under ultrasound irradiation

Abstract: Derivados de 3,4-dihidropirimidin-2-(1H)-onas foram sintetizados via uma reacao one-pot de tres componentes, com excelentes rendimentos em curtos tempos reacionais, usando aldeidos, acetoacetato de etila e ureia (ou tioureia) em liquidos ionicos a temperatura ambiente (RTILs) sob radiacao de ultrassom, sem adicao de catalisador. Um mecanismo sintetico plausivel foi postulado levando em consideracao o papel catalitico dos liquidos ionicos em promover a reacao. Os liquidos ionicos puderam ser reciclados no minimo seis vezes com boa retencao de atividade. Derivatives of 3,4-dihydropyrimidin-2-(1H)-ones were synthesized in excellent yields in short reaction time by one pot, three component reaction of aldehydes, ethyl acetoacetate and urea (or thiourea) in room temperature ionic liquids (RTILs) under ultrasound irradiation without any added catalyst. A plausible mechanistic pathway has been postulated based on the catalytic role of the ionic liquid in promoting the reaction. The ionic liquids could be recycled at least six times with retention of their activity.

Diclofenac abatement using modified solar photo-fenton process with ammonium iron(III) citrate

Abstract: The influence of pH on the degradation of the pharmaceutical diclofenac (DCF) by the solar/photo-Fenton process was investigated using ammonium iron(III) citrate complex (FecitNH4). Although the degradation efficiency decreased as the pH increased (in the pH range 5 to 8), the DCF concentration was lower than its limit of detection after 45 min irradiation while 77% of the total organic carbon was removed after 150 min irradiation at initial pH 7 (without further adjustment). A pseudo-first-order kinetics of DCF degradation was observed, which kinetic constant increased with the increase of the concentrations of FecitNH4 and H2O2. Lower DCF degradation was observed when present in a sewage treatment plant (STP) effluent sample, mainly due to the high concentration of carbonate and bicarbonate at pH 7. However, after adjusting the pH to 5, the DCF concentration was lower than its detection limit after 75 min irradiation.

Bromine and chlorine determination in cigarette tobacco using microwave-induced combustion and inductively coupled plasma optical emission spectrometry

Abstract: (NH4)2CO3 as absorbing solution and 5 min of reflux. Temperature during combustion was higher than 1400 °C and the residual carbon content in digest obtained after MIC was lower than 1%. Up to eight samples could be processed simultaneously and a single absorbing solution was suitable for both Br and Cl. Limit of quantification by MIC and further ICP OES determination was 12 and 6 µg g -1 for Br and Cl, respectively.

Input of organic matter in a large south american tropical estuary (Paranaguá Estuarine System, Brazil) indicated by sedimentary sterols and multivariate statistical approach

Abstract: O Estuario de Paranagua e um dos ambientes mais importantes da costa Sul-Americana. A ocupacao urbana, a pesca, o turismo, as industrias, a introducao de esgoto e o principal porto de exportacao de graos do Brasil sao fontes de impactos ambientais. As fontes de materia orgânica sedimentar foram avaliadas atraves das concentracoes de esterois, obtidas por cromatografia gasosa acoplada a espectrometria de massas (GC-MS). Os niveis de coprostanol foram comparativamente baixos, exceto proximo da cidade de Paranagua, onde as altas concentracoes indicaram contaminacao de esgotos. A analise de componentes principais mostrou a distincao entre os esterois de origem marinha (colesterol, colestanol, estigmasterol e campesterol), fecal (coprostanol e epicoprostanol) e aportes terrigenos (β-sitosterol). A composicao dos esterois nos sedimentos indicou predominio de materia orgânica marinha associada ao fitoplâncton. Contribuicoes terrigenas foram verificadas proximas a manguezais, rios e pequenas baias nao contaminadas. Contribuicao de esgotos e restrita ao entorno da cidade de Paranagua. The Paranagua Estuarine System is one of the most important environments of the South American coast. Fishing, urban and tourist activities, industries, sewage and the main shipping port for the export of grains in Brazil are sources of environmental impacts. The sources of sedimentary organic matter were evaluated by sterol concentrations which were obtained by gas chromatography with a mass spectrometer (GC-MS). The coprostanol levels were comparatively low, except at sites close to Paranagua City, where high concentrations have shown sewage contamination. The principal component analysis showed the distinction between sterols from marine (cholesterol, cholestanol, stigmasterol and campesterol), fecal (coprostanol and epicoprostanol) and terrigenous inputs (β-sitosterol). The sterol composition of the sediments indicated that the estuary system is an embayment dominated by inputs of marine organic matter associated with phytoplankton. Terrestrial inputs were detected only at sites close to mangroves, uncontaminated rivers and semi-closed inlets. Fecal input is restricted around Paranagua City.

Preparation and characterization of a chemically sulfated cashew gum polysaccharide

Abstract: -1 . The degrees of substitution were 0.02, 0.24 and 0.88 determined from the sulfur percentage. 1D and 2D nuclear magnetic resonance (NMR) data showed that the sulfation occurred at primary carbons. An increase of at least 4% of the solution viscosity was observed due to sulfation. The thermal gravimetric curves (TGA) indicate that the derivatives are stable up to ca. 200 °C. The sulfated CG is compared to carboxymethylated CG in order to verify the possibility of the use of the former in the preparation of polyelectrolyte complexes; the latter is already being used for this application.

Phenylpropanoid substituted flavan-3-ols from Trichilia catigua and their in vitro antioxidative activity

Abstract: The new phenylpropanoid substituted flavan-3-ol apocynin E, together with eight known compounds, epicatechin, procyanidin B2, procyanidin B4, procyanidin C1, cinchonain Ia, cinchonain Ib, cinchonain IIb, and cinchonain IIa were isolated from an acetone-H2O extract of the air-dried stem bark of Trichilia catigua. The cinchonain Ia e Ib were reevaluated to its estereochemistry. All the compounds were characterized by spectroscopic analysis including 1D and 2D nuclear magnetic resonance (NMR) and mass spectrometry (MS) of their peracetate derivatives. The absolute configuration of the phenylpropanoid moiety was determined by circular dichroism (CD) spectra and by analyzing the anisotropic effects in the Dreiding model and nuclear Overhauser effect (NOESY NMR) experiments. The nine isolated compounds showed higher radical scavenging activity and reducing power than ascorbic acid and Trolox in the free-radical 2,2-diphenyl-1-picrylhydrazyl and Fe3+-Fe2+ reduction assay systems.

Effect of the molecular weight on the physicochemical properties of poly(lactic acid) nanoparticles and on the amount of ovalbumin adsorption

Abstract: Poly(lactic acid) (PLA) nanoparticles were prepared to be used as potential platform for vaccine systems. Commercial high molecular weight PLA (PLAHMW) with Mw 1.5 × 105 and low molecular weight poly(lactic acid) (PLALMW) with Mw 9.3 × 103 were obtained by direct polycondensation from D,L lactic acid and used to prepare nanoparticles by solvent displacement method. The effect of the molecular weight on the physicochemical properties of the polymers, on the nanoparticles dispersions and the amount of ovalbumin (OVA) adsorption was studied. The PLAHMW and PLALMW were characterized by Fourier transformed infrared spectroscopy (FTIR), thermogravimetrical analysis (TGA), modulated temperature differential scanning calorimetry (MTDSC) and gel permeation chromatography (GPC). The particle size distribution and ζ-potential of the obtained dispersions were measured by dynamic light scattering (DLS) and electroacoustic spectroscopy, respectively. The ovalbumin adsorption on nanoparticles was evaluated by the Bradford method. PLALMW dispersion showed lower ζ-potential values and larger sizes compared to PLAHMW dispersion. A minor OVA adsorption was achieved for PLALMW.

Chitosan/siloxane hybrid polymer: synthesis, characterization and performance as a support for immobilizing enzyme

Abstract: A hybrid polymer derived from siloxane and chitosan was obtained by sol-gel technique using tetraethoxysilane (TEOS) as a precursor. The hybrid support was chemically modified with epichlorohydrin and used to immobilize lipase from Burkholderia cepacia. The hybrid SiO2-chitosan formed new macromolecular structure in which the inorganic particles are dispersed at the nanometer scale in the organic host matrix and bounding through covalent bonds. A comparative study between free and immobilized lipase was provided in terms of pH, temperature, kinetic parameters and thermal stability. The pH for maximum hydrolysis activity shifted from 7.0 for the soluble lipase to 6.1 and the optimum temperature remained at 50 oC after immobilization. The patterns of heat stability indicated that the immobilization process provided the stabilization of the enzyme and the epoxy SiO2-chitosan derivative was almost 30-fold more stable than soluble lipase at 60 oC.