A formação profissional do técnico em química: caracterização das origens e necessidades atuais

This work reports the situation of technicians employed in chemical industries in Curitiba city, working in chemistry and related fields. The aim of this study is to characterize not only their work conditions, but also their social, economic, professional and educational profiles.

O ensino de química quântica e o computador na perspectiva de projetos

This paper aims to discuss and reflect about the use of computers in the teaching of Quantum Chemistry. A course on Computational Quantum Chemistry concentrating on Medicinal Chemistry projects was developed for undergraduate and graduate students. The results showed that students got more motivated and involved when there is an articulation between theory and practice. This work presents an alternative way to teach Theoretical Chemistry using projects.

Craqueamento térmico de alcanos: uma aula prática de química orgânica para a graduação

In this work we describe an experiment for the thermal cracking of octane and heptane and the qualitative analyses of the products using the Baeyer test for unsaturated compounds and gas chromatographic analyses. The experiment is very simple and requires one period of two hours and is suitable for undergraduate organic chemistry experimental courses.

Composição química da precipitação atmosférica no sul do Brasil: estudo preliminar

The present work is a preliminary study of total and wet precipitation in the Candiota region, RS. The samples were collected from January to June 2001 at four different sites. The following variables were analysed: pH, conductivity, alkalinity, Cl-, NO3-, F-, SO4(2-), Na+, K+, Mg2+, NH4+, Ca2+ and Zn, Cu, Fe, Al, Mn. The results showed slightly acidic precipitation and higher concentrations of NH4+, Na+, Cl- and SO4(2-). Factor analysis applied to the variables studied allowed identifying the major sources. Na+, Cl- and Mg2+ have their origin in sea salts and NH4+, Ca2+, K+, SO4(2-) and NO3- are from local anthropogenic sources.

La química de las aguas : los nutrientes

Capítol 7 del llibre 'Conceptos y técnicas en ecología fluvial' que es refereix a la composició de les aigües

Aplicação e modificação química da sílica gel obtida de areia

The silica gel was obtained from sand and its surface was modified with POCl3 to produce Si-Cl bonds on the silica surface. Ethylenediamine was covalently bonded onto the chlorinated silica surface. The adsorption of the chlorides of divalent cobalt, nickel and copper was qualitatively studied to show that the bonding of ethylenediamine onto the silica gel surface produces a solid base capable of chelating metal ions from solution. The experiments illustrate the extraction of silica gel, its reactivity, the development of modified surfaces and its application in removing metal ions from water and are deigned for undergraduate inorganic chemistry laboratories.

Análise de imagem em química analítica: empregando metodologias simples e didáticas para entender e prevenir o escurecimento de tecidos vegetais

A simple and didactic experiment was developed for image monitoring of the browning of fruit tissues caused by the enzyme polyphenol oxidase. The procedure, easy and inexpensive, is a valuable tool to teach and demonstrate the redox reaction between the enzyme and the natural polyphenols. To obtain the browning percentage for apple, pear and banana, digital photographs were employed, and the images were analyzed by means of Monte Carlo methods and digital analysis programs. The effects of several experimental conditions were studied, such as pH, light, temperature and the presence of oxygen or anti-oxidants. It was observed that each fruit presented a different condition that better minimized the oxidation process. The absence of oxygen and the application of a bissulphite solution were sufficient to keep the quality of all fruits tested.

Otimização da reação de interesterificação química do óleo de palma

The Brazilian market has been showing a growing concern with nutritional values of oil components of foods. Chemical interesterification is a promising alternative to the current processes of modifying the consistency of oils. Chemical interesterification of deodorized palm oil was studied on a laboratory scale. The best results were obtained with 0.4% MeONa and heating for 20 min at 100 °C. These conditions are based on the largest variation in triacylglycerols as compared to a control. The trisaturated values varied from 6.2 to 9.9%, showing that the consistency of the oil improved for it to be used in margarines, without the formation of trans isomers.

Química combinatória de materiais com análise por microdifração de raios X. Primeira parte: fundamentos

Combinatorial chemistry refers to techniques to rapidly fabricate tens, hundreds or even thousands of different micro samples. The analysis of the large number of samples generated by combinatorial methods requires highly efficient analytical methods. In this case, the challenges are due not only to the large number of samples to be analyzed, but also to the small amount of sample available for analysis. This paper describes the fundamentals of combinatorial chemical methods applied to discover of materials and the development in x-ray diffraction to analyze micro samples.

O impacto industrial na composição química das águas subterrâneas com enfoque de consumo humano (Rio Grande, RS)

The alteration in the quality of groundwater in the industrial zone of Brazil's southernmost state was assessed by a hydrogeochemical study. In 70-85% of the studied area, fluoride, nitrate and phosphate in groundwater surpass the maximum limits for human consumption according to Brazilian environmental legislation. The chemical spectrum of contaminants and their spatial distribution show that fertilizer production processes are responsible for groundwater pollution. The natural conditions of the region are not favorable for minimal protection against infiltration of pollutants into the aquifer.

Utilização de regressão multivariada para avaliação espectrofotométrica da demanda química de oxigênio em amostras de relevância ambiental

In this work, a partial least squares regression routine was used to develop a multivariate calibration model to predict the chemical oxygen demand (COD) in substrates of environmental relevance (paper effluents and landfill leachates) from UV-Vis spectral data. The calibration models permit the fast determination of the COD with typical relative errors lower by 10% with respect to the conventional methodology.

Taninos: uma abordagem da química à ecologia

Tannins are compounds of great interest in chemistry and ecology. They have various effects on food digestibility and the performance of animals. In this work, the chemistry, the biological activity and the ecology of tannins are examined. A brief discussion of several analytical methods for the determination of tannins is presented.

Polímeros biomiméticos em química analítica. Parte 1: preparo e aplicações de MIP ("Molecularly Imprinted Polymers") em técnicas de extração e separação

MIPs are synthetic polymers that are used as biomimetic materials simulating the mechanism verified in natural entities such as antibodies and enzymes. Although MIPs have been successfully used as an outstanding tool for enhancing the selectivity or different analytical approaches, such as separation science and electrochemical and optical sensors, several parameters must be optimized during their synthesis. Therefore, the state-of-the-art of MIP production as well as the different polymerization methods are discussed. The potential selectivity of MIPs in the extraction and separation techniques focusing mainly on environmental, clinical and pharmaceutical samples as applications for analytical purposes is presented.

Polímeros biomiméticos em química analítica. Parte 2: aplicações de MIP ("Molecularly Imprinted Polymers") no desenvolvimento de sensores químicos

The aim of this paper is the description of the strategies and advances in the use of MIP in the development of chemical sensors. MIP has been considered an emerging technology, which allows the synthesis of materials that can mimic some highly specific natural receptors such as antibodies and enzymes. In recent years a great number of publications have demonstrated a growth in their use as sensing phases in the construction of sensors . Thus, the MIP technology became very attractive as a promising analytical tool for the development of sensors.

Atualizando a química orgânica experimental da licenciatura

The present contribution describes three different modern experiments for possible adoption in undergraduate organic chemistry laboratories. These are: 1. electrocatalytic hydrogenation of benzaldehyde to benzyl alcohol; 2. identification of three volatile components, obtained from pineapple fruit, by mass spectrometry and 3. microwave mediated fast synthesis of N-(p-chlorophenyl)phthalamic acid from phthalic anhydride and p-chloroaniline under solvent-free conditions. The experiments can be executed in a short period of time, putting the undergraduate student in contact with a variety of topics in organic chemistry and several techniques of analysis, showing multidisciplinarity in organic chemistry.