Editorial O que esperamos das revistas da SBQ? Torresi, Susana I. Córdoba de Pardini, Vera L. Ferreira, Vitor F. |
Artigo Treatment of biodiesel wastewater by electrocoagulation/flotation process: investigation of operational parameters Meneses, Janaina Moreira de Vasconcelos, Robelsa de Fátima Fernandes, Thalys de Freitas Araújo, Gilmar Trindade de Abstract in English: Electrocoagulation/flotation process was applied to treat biodiesel wastewater using aluminium electrodes. Firstly, a literature survey was conducted to choose the process variables and then, operational parameters including initial pH, electrode distance and reaction time were tested. Experimental results showed the best parameter that can be used in a factorial design for further studies. The results indicate that electrocoagulation/flotation is very efficient to reduce oil and grease, the effluent was very clear after treatment and small amount of sludge was produced. |
Artigo The molecular basis of anti-inflammatory action of the oleanolic and ursolic acids on cyclooxygenase isoforms by docking and molecular dynamics Magalhães, Wendell Santos Corrêa, Célia Maria Alencastro, Ricardo Bicca de Nagem, Tanus Jorge Abstract in English: The triterpenoids oleanolic (OA) and ursolic (UA) acids show non-selective antiinflamatory activity in vitro for cyclooxygenase (COX) isoforms. 3D conformations of OA and UA, with three possible orientations (1, 1' and 2) in the active site of isoforms COX, obtained by docking, were submitted to molecular dynamics. The results show that orientation 2 of the OA in COX-2 is more favorable because orientation 1 moved away from the active site. The carboxylate group of OA interact by hydrogen bonds with Ser353 and with Phe357 and Leu359, mediated by water, while hydroxyl in C-3 interact by hydrogen bond, mediated by water, with Tyr385. |
Artigo Lead distribution and isotope signature in bottom sediments of Guama River and Guajara Bay (Belem - Para) Santos, Suziane Nascimento Lafon, Jean Michel Corrêa, José Augusto Martins Babinski, Marly Dias, Fabiana Ferrari Taddei, Maria Helena Tirolo Abstract in English: Lead analyses in bottom sediments from the hydrographic system of Belem (Para) indicated low contents of this metal for the sediments from the Guama river, with no significant anthropogenic contribution. A concentration of 18.1 ± 1.5 mg kg-1 and 206Pb/207Pb isotopic signature of 1.196 ± 0.002 are assigned for Pb from natural sources. On the other hand, the significant increase of Pb contents in the sediments from the Guajará bay, together with the decrease of 206Pb/207Pb ratios (1.172 < 206Pb/207Pb < 1.188) point to an anthropogenic lead contribution, originated by the industrial and urban activities of the city of Belem. |
Artigo Spectroscopic studies of composite obtained from solid state reaction between a mononuclear vanadium(IV) complex and kaolinite Rezende, Edivaltris I. P. De Mangrich, Antonio S. Mangoni, Ana P. Scarpellini, Marciela Casellato, Annelise Fernández, Tatiana L. Abstract in English: The use of probes, such as paramagnetic species diluted in diamagnetic materials in EPR spectroscopy, and mathematical tools such, as the Kubelka-Munk function in DRUV-VIS spectroscopy are strategies in the analysis of complex mixtures of solid materials. The results obtained here show that the solid state reaction between the complex, [VO(acac)(BMIMAPY)] [ClO4], BMIMAPY = [(bis(1-methylimidazole-2-yl)methyl)(2-(pyridyl-2-yl)ethyl) amine] and acac = acetilacetonate, with kaolinite turns possible to obtain anisotropic EPR spectrum of the complex with a reasonable level of resolution. The study by DRUV-VIS using the method of second derivative mode of the Kubelka-Munk function revealed new complex structural arrangements, a solid hitherto unknown. |
Artigo Comparative studies on the characterization of biodegradable cassava starch films containing mango and acerola pulps Souza, Carolina Oliveira de Silva, Luciana Tosta Druzian, Janice Izabel Abstract in English: Most compounds reinforcements have been used to improve thermals, mechanical and barrier properties of biopolymers films, whose performance is usually poor when compared to those of synthetic polymers. Biodegradables films have been developed by adding mango and acerola pulps in different concentrations (0-17,1% w/w) as antioxidants active compounds to cassava starch based biodegradable films. The effect of pulps was studied in terms of tensile properties, water vapor permeability, DSC, among other analysis of the films. The study demonstrated that the properties of cassava starch biodegradable films can be significantly altered through of incorporation mango and acerola pulps. |
Artigo Use of heterogeneous CaO and SnO2 catalysts supported on rice husk ash to produce biodiesel Soares, Ana Brígida Silva, Paulo Roberto Nagipe da Stumbo, Alexandre Moura Freitas, Jair C. C. Abstract in English: Silica obtained from rice husk after acid leaching and calcination was compared to commercial silica as a catalyst support. CaO and SnO2 catalysts were prepared by impregnation and tested in the transesterification of soybean oil and the esterification of oleic acid. CaO catalysts showed basic character and were the most active for transesterification, whereas SnO2 catalysts were acid and the most effective for esterification. In both cases the performances of the catalysts prepared with rice husk ash and commercial silica were similar. These results demonstrate that rice husk is a cost-effective and environmentally-friendly source of silica that can be used as a catalyst support. |
Artigo Analytical aspects of the flame ionization detector response of fatty acid esters in biodiesels and foods Visentainer, Jesui Vergilio Abstract in English: The analysis of fatty acid (FA) esters by gas chromatography and flame ionization detector (FID) normally uses the normalization method. However, if one FA is wrongly estimated, the results could be greatly affected. In this study, methodologies using internal standards and correction factors for the FID response are described. The results show that by using theoretical correction factors associated to the internal standardization, the quantitative analyses of the FAs are expressed in mass, increasing the accuracy and facilitating the interpretation and comparison of the results for foods and biodiesels. |
Thermodynamic study of the solubility of triclocarban in ethanol + propylene glycol mixtures Holguín, Andres R. Delgado, Daniel R. Martínez, Fleming Abstract in English: By using the van't Hoff and Gibbs equations the apparent thermodynamic functions Gibbs energy, enthalpy, and entropy of solution for triclocarban in ethanol + propylene glycol mixtures were evaluated from solubility data determined at temperatures from (293.15 to 313.15) K. The drug solubility was greatest in the mixture with 0.60 in mass fraction of ethanol and lowest in neat propylene glycol at almost all the temperatures studied. Non-linear enthalpy-entropy compensation is found indicating apparently different mechanisms of the solution process according to the mixtures composition. |
Evaluation of hard gelatin capsules and hydroxypropyl methylcellulose containing ampicillin Weigert, Graziella Gonçalves Ineu, Aniéle Posser Gomes, Patrícia Abstract in English: This study aims to develop and evaluate formulations containing ampicillin in capsules of gelatin and hydroxypropyl methylcellulose (HPMC). Two formulations (A and B) were developed. The final product quality was evaluated by testing for quality control and the results were in agreement with the Brazilian Pharmacopoeia. The formulations with HPMC capsules showed lower percentages of drug dissolved (99.67%, HPMC-A and 87.70%, HPMC-B) than the gelatin (100.18%, GEL-A and 101.16% GEL-B). Because of the delay of the ampicillin release observed in the dissolution profiles, it becomes necessary to evaluate the drugs that can be conditioned in the HPMC capsules. |
Artigo Thermal aging effect in oxi-reduction properties and catalytic activity of CZ and Pd-CZ catalyst Silva, Daniela Cruz Damasceno da Zotin, Fátima Maria Zanon Neumann, Reiner Hori, Carla Eponina Cardoso, Mauri José Baldini Abstract in English: Automotive catalyst, using in Brazil since 1992, is a essential technology for vehicular emissions control. Noble metals are the active phase of these catalysts, and cerium zirconium mixed oxides (CZ), responsibles for the oxygen storage capacity (OSC), one of the most important aspect for the operational performance of the catalyst. In this context, the oxireduction properties analysis of CZ and Pd/CZ (palladium supported in CZ) system are the objective of this study, as well as, the impact of the thermal aging in the OSC. Aging consisted of treatments at 900 or 1200 °C, for 12 or 36 h, in oxidizing condition. |
Poly(ethylene-co-methyl acrylate)/poly(caprolactone) triol blends for drug delivery systems: characterization and drug release Kanis, Luiz A. Soldi, Valdir Abstract in English: Poly(ethylene-co-methyl acrylate) (EMA) and poly (caprolactone) triol (PCL-T) blends, a biodegradable aliphatic polyester with low molecular weight and moderate water solubility containing diltiazem hydrochloride (DZ) were studied in terms of the thermal and morphological properties, and drug release mechanism. An increase in the PCL-T content in the EMA/PCL-T/DZ films decreased the degree of DZ crystallinity. Drug release from these films is temperature-dependent, and it is possible to modify the drug release rate by adjusting the EMA/PCL-T composition of the blends. The mechanism of drug release is governed by PCL-T melting and PCL-T leaching from EMA matrix. |
Artigo Thermodynamic modeling for solvent extraction of metals divalent in sulphate media using D2EHPA Sousa Junior, Clenilson da Silva Ximenes, Dalton de Sousa Nascimento, Marisa Nascimento, Karina Rodrigues Paiva Ranauro do Cunha, Osvaldo Galvão Caldas da Abstract in English: The extraction of divalent metals (Mn2+, Ni2+, Co2+ and Cu2+) in the system MSO4 - H2SO4 - H2O - D2EHPA in isoparaffin (17/21) was studied by a thermodynamic model based on chemical equilibria with mass and charge balance equations. The activity coefficients of all solutes in the aqueous phase were calculated by Davies equation. By applying this model, the equilibrium concentrations of solutes were calculated from de concentration of divalent metals and pH. The predicted distribution coefficients for the divalents metals were in good agreement with experimental results. |
Artigo Sequential extraction of zinc and copper in soils treated with sewage sludge and municipal solid waste compost Souza, Regilene Angélica da Silva Bissani, Carlos Alberto Tedesco, Marino José Fontoura, Rogério Chimanski da Abstract in English: This work aimed to access the contents and chemical forms and to estimate mobility and availability of cooper and zinc in samples from two soils (Haplortox and Paleudult) previously treated with doses of sewage sludge (SS) and municipal solid waste compost (MSWC), besides a control treatment. Largest percentages of Cu and Zn were determined in the organic matter fraction. Zn showed higher percentages of soluble and exchangeable fractions than Cu. Treatments with SS showed higher potential of Cu and Zn availability. Modifications in soil attributes due to residue application affected metal mobility and availability indexes. |
Artigo Biodiesel classification in the visible region Véras, Germano Brito, Anna Luiza Bizerra de Silva, Adenilton Camilo da Silva, Priscila da Costa, Gean Bezerra da Félix, Lorena Cristina Nóbrega Fernandes, David Douglas de Sousa Fontes, Marcelo Marques de Abstract in English: Classification of biodiesel by oilseed type using pattern recognition techniques is described. The spectra of the samples were performed in the Visible region, requiring noise removal by use of a first derivative by the Savitzky-Golay method, employing a second-order polynomial and a window of 21 points. The characterization of biodiesel was performed using HCA, PCA and SIMCA. For HCA and PCA methods, one can observe the separation of each group of biodiesel in a spectral region of 405-500 nm. SIMCA model was used in a test group composed of 28 spectral measurements and no errors are obtained. |
Artigo Photodecomposition by ultraviolet exposure of positive photoresists Borges, Bruno Gabriel Alves Leite Rocco, Maria Luiza Miranda Pinho, Roberto Rosas Lima, Carlos Raimundo Abstract in English: Positive photoresists are widely used in lithographic process in microelectronics and in optics for the fabrication of relief components. With the aim of identifying molecular modifications among positive photoresists unexposed and previously exposed to ultraviolet light the electron stimulated ion desorption technique coupled to time-of-flight mass spectrometry was employed in the study of the AZ-1518 photoresist. Mass spectra were obtained as a function of the electron beam energy, showing specific changes related to the photochemical decomposition of the photoresist. This reinforces the applicability of the technique to investigate and characterize structural changes in photosensitive materials. |
Artigo Sesquiterpenes from the seeds of Guarea guidonia (Meliaceae) Soares, Luzinátia Ramos Silva, Alene Cortes de Queiroz e Freire, Talita Vilalva Garcez, Fernanda Rodrigues Garcez, Walmir Silva Abstract in English: Two new sesquiterpenes 6α-ethoxyeudesm-4(15)-en-1β-ol (1) and (7R*)-5-epi-opposit-4(15)-ene-1β,7-diol (7) were isolated from the seeds of a specimen of Guarea guidonia (Meliaceae). Five other known sesquiterpenes, eudesm-4(15)-ene-1β,6α-diol (2), 5-epi-eudesm-4(15)-ene-1β,6β-diol (3), eudesm-4(15)-ene-1β,5α-diol (4), eudesm-4(15),7-dien-1β-ol (5) and (7R*)-opposit-4(15)-ene-1β,7-diol (6), were also isolated in this work. Their structures were determined on the basis of spectral data (MS, IR, and NMR-1D and 2D) and subsequent comparisons with the literature. The substances 3, 4 and 6 are reported for the first time in Meliaceae and 5 for the first time in the genus Guarea. |
A quantitative validated method using liquid chromatography and chemometric analysis for evaluation of raw material oF Maytenus ilicifolia (Schrad.) Planch., Celastraceae Beltrame, Flávio Luís Mainardes, Rubiana Mara Khalil, Najeh Maissar Prestes, Rosilene Aparecida Nogueira, Alessandro Demiate, Ivo Mottin Cass, Quezia Bezerra Abstract in English: The hydroalcoholic extracts prepared from standard leaves of Maytenus ilicifolia and commercial samples of espinheira-santa were evaluated qualitatively (fingerprinting) and quantitatively. In this paper, fingerprinting chromatogram coupled with Principal Component Analysis (PCA) is described for the metabolomic analysis of standard and commercial espinheira-santa samples. The epicatechin standard was used as an external standard for the development and validation of a quantitative method for the analysis in herbal medicines using a photo diode array detector. This method has been applied for quantification of epicatechin in commercialized herbal medicines sold as espinheira-santa in Brazil and in the standard sample of M. ilicifolia. |
Artigo Photoelectrochemical degradation of the herbicide bentazone on the carbon electrodes modified by TiO2 Bessegato, Guilherme Garcia Santos, Valderi Pacheco Lindino, Cleber Antonio Abstract in English: This work involved the study of degradation of the herbicide bentazone in aqueous solution by different routes, in order to search a method that generates safe products to the environment. It was tested electrochemical polarization methods involving positive and negative potential, irradiation with UV light and deposition of TiO2 on the electrode surface, seeking a catalytic effect. After different times of degradation, aliquots were removed and the scan of molecular absorption spectrum of UV-Vis was performed. From the spectra decay of bentazone, the kinetics of different processes was accompanied and the rate constants were determined. |
Extraction and isolation of dictamnine, obacunone and fraxinellone from Dictamnus dasycarpus Turcz. by supercritical fluid extraction and high-speed counter-current chromatography Wang, Daijie Lin, Yunliang Lin, Xiaojing Geng, Yanling Wang, Xiao Zhang, Jinjie Qiu, Jiying Abstract in English: Supercritical fluid extraction was used to extract active compounds from the Chinese traditional medicinal D. dasycarpus under the pressure of 30 MPa and temperature of 45 ºC. Further separation and purification was established by high-speed counter-current chromatography (HSCCC) with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (1:0.8:1.3:0.9, volume ratio). The separation yielded a total of 47 mg of dictamnine, 24 mg of obacunone and 83 mg of fraxinellone from 1.0 g of the crude extract in one step separation with the purity of 99.2, 98.4 and 99.0%, respectively, as determined by HPLC. The chemical structures of these compounds were identified by ESI-MS, IR, ¹H-NMR and 13C-NMR. |
Evaluation of the performance of a castor-oil based formulation in limiting pesticide residues in strawberry crops Galhiane, Mário Sérgio Rissato, Sandra Regina Santos, Lucídio de Sousa Chierice, Gilberto Orivaldo Almeida, Marcos Vinícius de Fumis, Terezinha Chechim, Inês Sampaio, Aloísio Costa Abstract in English: A study was made to evaluate the effect of a castor oil-based detergent on strawberry crops treated with different classes of pesticides, namely deltamethrin, folpet, tebuconazole, abamectin and mancozeb, in a controlled environment. Experimental crops of greenhouse strawberries were cultivated in five different ways with control groups using pesticides and castor oil-based detergent. The results showed that the group 2, which was treated with castor oil-based detergent, presented the lowest amount of pesticide residues and the highest quality of fruit produced. |
Artigo Oscillatory dynamics in systems containing bromate and 1,4-cyclohexanedione in acidic media: I. The effect of temperature Oliveira, Hyrla C. L. Oliveira, Tatiane B. Varela, Hamilton Abstract in English: We present in this work the influence of temperature on the dynamics of homogeneous chemical systems containing bromate and 1,4-cyclohexanedione (1,4-CHD) in acidic media. In particular, the following systems were studied: bromate/1,4-CHD/acid, bromate/1,4-CHD/ferroin/acid and bromate/1,4-CHD/trisbipyridine ruthenium/acid. Investigations were carried out by means of an electrochemical probe, at five temperatures between 5 and 45 °C. Activation energies (Ea) were estimated in different ways for the pre-oscillatory and oscillatory regimes. In any case, the Ea was found to depend on the catalyst, composition and initial concentrations. In addition, it was observed that ferroin and trisbipyridine ruthenium act as catalysts only during the transition between the induction period and oscillatory regime. |
Artigo SAXS and DSC evaluation of interactions between H2O and Renex-100 Campos, Daniella Dias Palombino de Cassu, Silvana Navarro Garcia, Renata Batista Rivero Queiroz, Hiure Anderson Alves da Silva Gonçalves, Rene Francisco Boschi Kawachi, Elizabete Yoshie Abstract in English: The aggregation behavior of the non-ionic surfactant Renex-100 in aqueous solutions and mesophases was evaluated by SAXS in a wide range of concentrations, between 20 and 30 °C. Complementary, water interactions were defined by DSC curves around 0°C. SAXS showed that the system undergoes the following phase transitions, from diluted to concentrated aqueous solutions: 1) isotropic solution of Renex aggregates; 2) hexagonal mesophase; 3) lamellar mesophase; and 4) isotropic solution. DSC analysis indicated the presence of interfacial water above 70wt%, which agreed with the segregation of free water to form the structural mesophases observed by SAXS bellow this concentration. |
Revisão Exotic nuclei and synthesis of chemical elements Teruya, Nilton Duarte, Sérgio Barbosa Abstract in English: We have around ninety chemical elements available in nature, which were produced mainly by nuclear reactions inside stars. The fusion reactions are the main synthesis process which generates the light and intermediate masses elements. The synthesis begins with the hydrogen burning reaching the region of iron mass nuclei. Heavier elements are synthesized by neutron capture processes, forming exotic nuclei with large neutron excess. These systems present characteristics very different from nuclei inside of stable atoms; they only occur in particular astrophysical environments or are produced artificially in special laboratory conditions. This work discusses some properties of the exotic nuclei and how they participate in the synthesis of elements. |
Revisão Treatments of the effluents generated in the biodiesel production Palomino-Romero, Joel A. Leite, Otávio M. Barrios Eguiluz, Katlin I. Salazar-Banda, Giancarlo R. Silva, Daniel P. Cavalcanti, Eliane B. Abstract in English: The wastewaters from biodiesel production contain as primarily wastes sodium or potassium soaps, fatty acids, glycerin, alcohol and other contaminants. In general, these waters are chemically unsuitable for release to any water body, so, it is necessary the adoption of techniques for the treatment of this effluent. In this review, electrochemical, biological, physicochemical, and combined treatments reported for the removal of the wastewater containing pollutants come from biodiesel production have been summarized. In addition, the recovery, the reuse, the energy production and the synthesis of new compounds from the organic matter contained in this kind of effluent are also reviewed. |
Nota técnica Development of a homemade device for desalination of brackish water using umbu seeds (Spondias tuberosa Arruda Câmara) Menezes, Joilma da S. Campos, Vânia P. Costa, Tadeu A. de C. Abstract in English: The goal of this work was to develop a homemade device to desalinate brackish water, using biological material like seeds from different plant species of the semi arid regions. Umbu seeds (Spondias tuberosa Arruda Câmara) were found to be the most appropriate material, removing a higher quantity of salt from the water compared to the other tested materials. The salt content in 1 L of brackish water typical of the region can be removed with only 1 g of the material, if the water is heated to 50 °C and it may also lower the water hardness, achieving drinking water standards. |
Development of a simple UV-spectrophotometric method for the determination of lansoprazole and study of its degradation profile Okram, Zenita Devi Kanakapura, Basavaiah Jagannathamurthy, Ramesh Pavagada Basavaiah, Vinay Kanakapura Abstract in English: A UV-spectrophotometric method is described for the determination of lansoprazole (LAN). The method is based on the measurement of the absorbance of LAN solution in acetonitrile at 281 nm. The system obeyed Beer's law over the concentration range of 1.25-25.0 µg/mL. The degradation behavior of LAN was investigated under dry heat treatment, UV-degradation, acid hydrolysis, alkali hydrolysis and oxidation; and found to degrade extensively under acid hydrolysis, alkali hydrolysis and oxidation. The method was applied to the determination of LAN in capsule and the results were statistically compared with those of the reference method by applying Student's t-test and F-test. |
Studies on the development of spectrophotometric method for the determination of haloperidol in pharmaceutical preparations Rahman, Nafisur Khatoon, Asma Rahman, Habibur Abstract in English: A spectrophotometric method based on the formation of ion-pair complex between haloperidol and eriochrome black T (EBT) at pH 1.85 has been described. The formed complex was extracted quantitatively into chloroform and measured at 510 nm. Infra red (IR) studies were performed to confirm the formation of ion-pair complex. Beer's law was obeyed in the concentration range of 2.0-9.0 µg mL-1 with molar absorptivity of 2.67 × 10(4) L mol-1 cm-1. The detection limit was found to be 0.18 µg mL-1. Statistical comparison of the results of the proposed method with those of the reference method shows excellent agreement and indicates no significant difference in accuracy and precision. |
Nota técnica Recovery of iodine compounds from laboratory chemicals and solutions Santos, Vanessa da Matta dos Afonso, Júlio Carlos Abstract in English: This work presents simple routes to recover iodine compounds from oxidized laboratory chemicals and aqueous solutions (HI and KI) used in laboratory chemistry classes. These routes are based on the oxidation of iodide ions (I-) to iodine (I2) by an oxidant (H2O2) or reduction of oxidized iodine by red phosphorus or hydrazine. Both routes presented high yields. The oxidative route is of general use whereas the reductive one is appropriate for restoring original iodine reagents. Final wastes were generated in low amounts. This work is appropriate for teaching many laboratory techniques (e.g., distillation, titration and filtration) in the chemical laboratory. |
Nota técnica Serum quantification of vitamin C by HPLC-UV and stability study Baierle, Marília Bairros, André de Moreira, Ana Paula Bulcão, Rachel Roehrs, Miguel Freitas, Fernando de Durgante, Juliano Brucker, Natália Charão, Mariele Garcia, Solange Cristina Abstract in English: Vitamin C, an exogenous antioxidant, is essential to human health. In this study, a method was validated to serum vitamin C quantification by HPLC-UV. Its stability with and without the use of tris [2-carboxy-ethyl] phosphine hydrochloride (TCEP), at -20 and -80 °C, in serum and supernatant were also evaluated. Analysis showed r² > 0.99, precision CV% < 15% and % bias < 15%, being linear, precise and accurate. The stability test revealed that using TCEP in serum storage at -20 and -80 °C or in supernatant at -80 °C the vitamin C levels remain stable for 30 and 12 days, respectively. |
A validated method using RP-HPLC for quantification of reserpine in the Brazilian tree Rauvolfia sellowii Müll. Arg. (Apocynaceae) Baratto, Leopoldo C. Campos, Francinete Ramos Pontarolo, Roberto Santos, Cid A. de Moraes Abstract in English: This study describes a simple, fast and reproducible method using RP-HPLC-UV, in a gradient system, for quantification of reserpine in Rauvolfia sellowii stem bark. The analysis were carried out on a C18 column; mobile phase was water and acetonitrile, and separations were carried out in 10 min, flow rate of 1.0 mL min-1, 25 ºC and 268 nm. The validation data showed that the method was specific, accurate, precise and robust. Results were linear over a range of 0.625-40.0 μg mL-1, and the mean recovery was 95.1%. The amount of reserpine found in the dried stem bark was 0.01% (m/m). |
High performance thin layer chromatographic determination of nifedipine in human serum after liquid-liquid extraction Mennickent, Sigrid Contreras, Jonathan Schulz, Berta Diego, Marta de Vega, Mario Abstract in English: A method using HPTLC for quantitation of nifedipine in serum was developed and validated. It includes a liquid-liquid extraction, and carbamazepine as internal standard. Chloroform: ethyl acetate: cyclohexane (19:2:2, v/v/v) was the mobile phase. The method showed good relationship (r = 0.996) (2.00 to 25.00 ng/band, corresponding to 0.02 and 0.25 ng/µL in serum). The % RSD of intra-assay and inter-assay, were between 0.57 and 3.56 and 1.16 to 3.60, respectively. LOD and LOQ were 0.72 and 0.86 ng/band, respectively. The recovery values were between 93 and 102%. Rf for nifedipine and carbamazepine were 0.31 and 0.10, respectively. |
Educação The investigation rice husk ash as a stationary phase in chromatography: a proposal of experimental class in undergraduate courses Freitas Filho, João R. de Freitas, Jucleiton J. Rufino de Silva, Ladjane Pereira da Freitas, Juliano C. Rufino Abstract in English: This article describes an experiment that involves the extraction and separation of the pigments of spinach extract by column chromatography using the silica obtained from rice husk ash as a stationary phase. The experimental procedure is very simple to apply in the chemistry laboratory, and allowed to illustrate some concepts of organic chemistry: structure of organic molecules, solubility, polarity, extraction, partition coefficient, adsorption and retention factor (Rf), as well as objectives and fundamentals of chromatographic methods. The experiment can be carried out in a 4 h period. |
Educação Investigating the presence of the history of science in university general chemistry textbooks Fernandes, Maria Angélica Moreira Porto, Paulo Alves Abstract in English: This paper aims at analyzing the history of science content of three general chemistry textbooks used in Brazilian universities: the translations of Kotz and Treichel's Chemistry & Chemical Reactivity, Atkins and Jones's Chemical Principles, and Garritz and Chamizo's Química. Results revealed different trends for the inclusion of history of science in chemistry teaching. Kotz & Treichel and Atkins & Jones used history mainly as curiosity and ornament. Garritz & Chamizo adopted the historical approach as one of the organizing axis of their textbook. Nevertheless, the historical content of the three textbooks may be criticized from current historiographical standpoint. |
Educação The experimental work in the Chemistry teaching Lôbo, Soraia Freaza Abstract in English: This article deals with conceptions of the experimental work in the Chemistry teaching, developed among teachers and students. The research was carried out using qualitative methodology, based on Gaston Bachelard's thoughts. The results showed dispersion of conceptions among both students and teachers. This dispersion, interpreted as a profile of conceptions, was discussed based on the notions of Bachelard's epistemological profile and Mortimer's conceptual profile. This work points out the need to rethinking and finding new directions for experimental activities in the training courses for Chemistry teachers, in order to meet Chemistry educators' social goals. |
Educação Enzymatic reduction of 4-(dimethylamino)benzaldehyde with carrot bits (Daucus carota): a simple experiment for understading biocatalysis Omori, Álvaro Takeo Portas, Viviane Barbosa Oliveira, Camila de Souza de Abstract in English: The present paper describes a simple, low-costly and environmentally friendly procedure for reduction of 4-(dimethylamino)benzaldehyde using carrot bits in water. This interdisciplinary experiment can be used to introduce the concepts of biocatalysis and green chemistry to undergraduate students. |
The contributions of Henri Victor Regnault in the context of organic chemistry of the first half of the nineteenth century Reif-Acherman, Simón Abstract in English: A very little known aspect of the scientific career of Regnault is his contribution to the emerging organic chemistry in the first half of the nineteenth century. The purpose of this article is not only to describe two of his most important researches in this field, as were the discovery of two series of halogenated derivates of certain organic compounds and the precise identification of some of the then recently discovered alkaloids, but also the main features that identified his research method. With the involvement in these subjects, Regnault unintentionally positioned himself in the midst of some of the polemics about the classification of organic compounds that characterized this age of science. |