Simulações computacionais e ferramentas de modelização em educação química: uma revisão de literatura publicada

This article presents a review of published literature concerning the use of computer simulations and modeling tools in Chemical Education. The findings about the possibilities of their application in the Chemistry curriculum, their effective implementation, the teaching methods involved, the research methodology and also the instruments of evaluation that were used and their results were described and analyzed. The need to develop adequate theory support to educators who want to start using this new technology in their Chemistry classes became evident along the research, as well as the lack of development of model perception among Chemistry educators and learners.

Especiação analítica de compostos de arsênio empregando métodos voltamétricos e polarográficos: uma revisão comparativa de suas principais vantagens e aplicações

This paper provides a review on voltammetric and polarographic methods for the speciation analysis of inorganic and organic arsenic compounds in different matrices. A discussion on the main advantages of electroanalytical methods in comparison with other analytical methods employed for arsenic speciation is presented. The mechanistic aspects of the most relevant techniques employing cathodic and anodic stripping voltammetry as well as polarographic methods published in the last twenty five years are summarized and discussed. The bibliographic references cited in this work were selected from the Web of Science (published by the ISI) and the main journals of analytical chemistry.

Complexos metálicos com o herbicida glifosato: revisão

We present studies involving metallic ions and the herbicide glyphosate. The metallic complexes of Cu(II), Zn(II), Mn(II), Ni(II), Cd(II), Pb(II), Cr(III), Fe(III), Co(III), ammonium, sodium, Ag(I), alkaline earth metals and of some lanthanides ions are described. The complexes are discussed in terms of their synthesis, identification, stability and structural properties, based on data from the current literature.

Síntese e reatividade de complexos platina-trifenilestibina: uma revisão bibliográfica

This article deals with synthesis and reactivity of complexes with triphenylstibine (SbPh3) as the ligand. A comparative study of analogous complexes of triphenylphosphine (PPh3) and triphenylarsine (AsPh3) with platinum in the oxidation states zero, two and four is included. The bibliographic revision includes publications since 1936, when the first Pt(II) complex with triphenylstibine was described.

Cafeína: revisão sobre métodos de análise

Gravimetric and Bailey-Andrew methods are tedious and provide inflated results. Spectrofotometry is adequate for caffeine analysis but is lengthy. Gas chromatography also is applied to the caffeine analysis but derivatization is needed. High performance liquid chromatography with ultraviolet detection (HPLC-UV) and reversed phase is simple and rapid for xanthine multianalysis. In HPLC-UV-gel permeation, organic solvents are not used. HPLC-mass spectrometry provides an unequivocal structural identification of xanthines. Capillary electrophoresis is fast and the solvent consumption is smaller than in HPLC. Chemometric methods offer an effective means for chemical data handling in multivariate analysis. Infrared spectroscopy alone or associated with chemometries could predict the caffeine content in a very accurate form. Electroanalytical methods are considered of low cost and easy application in caffeine analysis.

Biotransformação de limoneno: uma revisão das principais rotas metabólicas

There is considerable progress in the study of the biotransformation of limonene. Extensive research on the biotransformation of limonene has resulted in the elucidation of new metabolic pathways. Natural flavors can be produced via biotransformation, satisfying consumer demand for natural products. This review presents some elements concerning the biotransformation of limonene with emphasis on the metabolic pathways. Some comments are also made on problems related to biocatalysis as well as on the application of some compounds originating from the biotransformation of the inexpensive limonene.

Argilas especiais: argilas quimicamente modificadas - uma revisão

The simultaneous use of the specific values of some structural and chemical properties of clay minerals, such as kaolinite, montmorillonite and talc, allows the development of new properties for these materials, especially in relation to the external and internal microcrystal surfaces. These developments are very diversified for montmorillonite, due to the high specific surface area, expansible basal spacings, easy intercalation inside the 2:1 structural layers and a reversible and high cation exchance capacity. The review presents examples of chemical modifications on kaolins, montmorillonites (bentonites) and talcs.

Análise direta de sólidos por espectrometria de absorção atômica com atomização em forno de grafite: uma revisão

This is a review of direct analysis using solid sampling graphite furnace atomic absorption spectrometry. Greater emphasis is dedicated to sample preparation, sample homogeneity, calibration and its application to microanalysis and micro-homogeneity studies. The main advantages and some difficulties related to the applicability of this technique are discussed. A literature search on the application of solid sampling graphite furnace atomic absorption spectrometry in trace element determination in many kinds of samples, including biological, clinical, technological and environmental ones, is also presented.

Ensaios para determinar a (Bio)disponibilidade de chumbo em solos contaminados: revisão

Incidental ingestion of contaminated soils is a major route of Pb uptake by humans, especially by children. Lead speciation in soils controls its bioavailability. Bioavailability assessment requires the determination of the amount of absorbed lead if a contaminated soil is ingested. In vivo tests, which employ animals, are considered the best model to infer absorption of Pb. But they have some logistic limitations and several authors proposed in vitro methods, which simulate conditions of human digestion. Many of them present results which correlate with in vivo essays. Several authors consider in vitro tests a good and reliable alternative to infer lead bioavailability.

A produção do conhecimento sobre o ensino de química nas reuniões anuais da Sociedade Brasileira de Química: uma revisão

This paper discusses the Brazilian academic production on Chemical Education. The main source of information is the annual meeting of the Brazilian Chemical Society (RASBQ) covering the period 1999-2006. All the papers presented by the Division of Chemical Education of the RASBQ were reviewed to permit a discussion about the development of the area in Brazil. This bibliographical revision comprises the following aspects: year of presentation, Brazilian region and institution of production, scholastic level encompassed by the study, the kind of academic work (or research type) and thematic focus of the study.

Nanoestruturas em fotocatálise: uma revisão sobre estratégias de síntese de fotocatalisadores em escala nanométrica

Advanced oxidative processes (AOPs) are based on chemical processes that can generate free radicals, such as hydroxyl radicals (.OH) which are strong, non-selective oxidant species that react with the vast majority of organic compounds. Nanostructured semiconductors, especially titanium dioxide (TiO2) in the anatase phase, are well-established photocatalysts for this process, which have proved to be useful in the degradation of dyes, pesticides and other contaminants. Research in different strategies for the synthesis of nanostructured semiconductors, with particular characteristic is currently a topic of interest in many studies. Thus, this paper presents a review about various synthesis strategies of nanostructured photocatalysts.

Eletrodos modificados por hidróxido de níquel: um estudo de revisão sobre suas propriedades estruturais e eletroquímicas visando suas aplicações em eletrocatálise, eletrocromismo e baterias secundárias

The present review paper describes the main features of nickel hydroxide modified electrodes covering its structural and electrochemical behavior and the newest advances promoted by nanostructured architectures. Important aspects such as synthetic procedures and characterization techniques such as X-Ray diffraction, Raman and Infrared spectroscopy, Electronic Microscopy and many others are detailed herein. The most important aspect concerning nickel hydroxide is related to its great versatility covering different fields in electrochemical-based devices such as batteries, electrocatalytic systems and electrochromic electrodes, the fundamental issues of these devices are also commented. Finally, some of the newest advances achieved in each field by the incorporation of nanomaterials will be shown.

Catalisadores metalocênicos suportados para a produção de poliolefinas: revisão das estratégias de imobilização

The inadequacy of strategies used for the heterogeneization of metallocene catalysts is pointed out as one of the main causes of the lack of industrial employability of such polymerization catalysts. The main problems are the necessity of large quantity of MAO (cocatalyst) and the inability to control molecular mass distribution of the polymers. Based on this background, the main strategies for the heterogeneization of metallocenes are here reviewed. The advantages and disadvantages of each strategy are presented and discussed on theoretical and practical perspective. Considering the results reported on the different researches, outcomes of heterogeneization strategies are pointed out.

Uma revisão sobre o efeito Toms: o fenômeno onde macromoléculas atenuam a turbulência em um líquido

It is very well known that the addition of polymers to a liquid increases the shear viscosity of the solution. In other words, the polymer increases the dissipation of the flow energy. Contrarily, in turbulent flow, some particular macromolecules in very low concentration are able to produce large attenuation in the turbulence and thus, decreasing the dissipation of the energy. This article present a brief revision about macroscopic and molecular models used to explain this dynamic effect. Some of the experimental techniques used to quantify the attenuation of the turbulence and the main active substances are also discussed.

A intrigante bioquímica da niacina: uma revisão crítica

Niacin (nicotinamide, nicotinic acid) interferes on homeostasis, DNA regulation, signaling and longevity. Nicotinic acid reduces synthesis of lipoproteins-apo-B and increases HDL. Its antilipemic action in liver produces: 1) inhibition of DGAT2, with decreased triacylglycerol synthesis, 2) downregulation of the b-chain of adenosine triphosphate synthase, leading to reduced HDL-apo-A-I catabolism. Nicotinic acid could increase redox potential in vascular endothelium. HM74A receptor activation in macrophages would be responsible for the release of prostaglandins, causing flushing in epidermis. HM74A agonists could assist in identifying antilipemic agents. Extended release niacin in combination with statin appears to protect cardiovascular system of patients with low HDL.