Heavy metals and pesticides are usually associated with the main problems humankind has created in the natural environment. However, compounds with characteristics of essential macronutrients are causing serious environmental changes that could intensify, compromising the diversity of life on the planet. This is the case of nitrogen compounds, produced by industrial processes for use in intensive agriculture in addition to those unwittingly produced from human activities, available in excess in the environment. These compounds warrant greater attention from researchers in various fields of knowledge and public agencies for environmental control, toward minimizing their availability in the environment, thereby returning conditions closer to the natural environmental balance of the planet.

Trace element concentrations were measured in atmospheric particulate matter collected in 2009 and 2010, in a Brazilian region influenced by pre-harvest burning of sugar cane crops. For coarse particles, high concentrations of Al, Fe, K and Ca suggested that re-suspended soil dust was the main source of aerosol trace elements, subsequently confirmed by XRD analysis. High levels of K, Zn, As, Cd and Pb were found in fine particles, confirming the contribution of biomass burning and vehicle emissions, whereas Na, Al, K, Fe and Zn were the representative elements in ultrafine particles, influenced by a diversity of sources.

In this work, a rapid and simple method using capillary electrophoresis (CE) was developed for the determination of the benzoate, sorbate, methyl and propylparaben in foodstuffs. A running buffer consisting of 20 mmol L-1 (pH = 9.3) tetraborate enabled separation of the analytes in less than 5 min. The detector wavelength was set at 220 nm. The method was successfully applied to the analysis of sodas, sweeteners, sauces and juices. The range of preservatives found were from 478.5-466.6 mg kg-1 for methylparaben , 83.7-231.3 mg kg-1 for sorbate and 336.7-428.3 mg kg-1 for benzoate.

A maioria dos problemas de origem endodôntica tem um agente etiológico bacteriano. Assim, existe um interesse permanente em se buscar substâncias químicas mais efetivas e que possam substituir o PMCC ou os antibióticos como curativos de demora. Dentre as possíveis substâncias, o ozônio apresenta algumas características biológicas interessantes: ação bactericida, efeito debridante, estímulo a angiogênese, além do efeito oxidante. O propósito do presente estudo foi avaliar quimicamente a presença de ozônio nos óleos de girassol, rícino, oliva e amêndoas, além do propilenoglicol, bem como subproputos da ozonização, como formaldeído. Essas substâncias foram ozonizadas, inseridas em tubetes anestésicos vazios e esterilizados, e analisadas por meio do teste da reação entre ozônio e índigo, para determinação da presença de ozônio; e teste do ácido cromotrópico, para determinação da presença de formaldeído. Foi observado ausência total de ozônio em todas as amostras testadas, além da presença de formaldeído. A ação bactericida e curativa dos óleos ozonizados poderia ser atribuída aos produtos formados pela ozonização de óleos minerais, como o formaldeído, e não ao ozônio propriamente dito.

Most of the problems of endodontic origin have a bacterial etiological agent. Thus, there is a continued interest in seeking more effective chemical substances that can replace the camphorated paramonochiorophenol or antibiotics as intracanal medicaments. Among the possible substances, ozone has some interesting biological characteristics: bactericidal action, debriding effect, angiogenesis stimulation capacity and high oxidizing power. The purpose of this study was to chemically evaluate the presence of ozone in sunflower, castor, olive and almond oil, as well as in propylene glycol and byproducts of ozonation, such as formaldehyde. These compounds were ozonized, inserted into empty and sterile vials, and analyzed by testing the reaction between ozone and indigo, for determining the presence of ozone, and subjected to the chromotropic acid test for determining the presence of formaldehyde. It was observed complete absence of ozone in all samples tested and presence of formaldehyde. The bactericidal and healing action of ozonized oils could be attributed to products formed by the ozonation of mineral oils, such as formaldehyde, not to the ozone itself.

Índigo carmim forma complexos estáveis com diferentes íons e a constante de estabilidade dos complexos foi avaliada como log K igual 5,75; 5,00; 4,89 e 3,89, respectivamente, para os complexos com os íons Cu(II), Ni(II), Co(II) e Zn(II) em solução tampão carbonato 0,1 mol L-1, pH 10. A interação entre o íon Cu(II) e índigo carmin (IC) em meio alcalino resultou na formação do complexo Cu2(IC) monitorado por método espectrofotométrico, com razão estequiométrica entre o índigo carmim e o íon metálico de 2:1 (metal-ligante). O método relatado também tem sido testado com sucesso para determinação de cobre em compostos farmacêuticos à base de cobre-gliconato sem qualquer pré-tratamento.

Indigo carmine forms a stable complex with different ions, and the stability constant of the complexes were evaluated as log K equal to 5.75; 5.00; 4.89 and 3.89 for complexes with Cu(II), Ni(II), Co(II) and Zn(II) ions, respectively, in 0.1 mol L-1 carbonate buffer solution at pH 10. The interaction between Cu(II) ions and indigo carmine (IC) in alkaline medium resulted in the formation of the Cu2(IC) complex, measured by the spectrophotometric method, with a stoichiometric ratio between indigo carmine and metal ions of 2:1 (metal-ligand). The reported method has also been successfully tested for determination of copper in pharmaceutical compounds based on copper-gluconate without pre-treatment.

The seasonal behavior of NO2 concentration shows a maximum occurring during sugarcane crop and this suggests that the biomass burning is significant source of emission at this time of the year. Along the day, the variation of the NO2 showed a decrease during the increased sunlight and an increase thereafter, caused by occurrence of photochemical reactions. Measurements of NO2 were done inside of residential and industrial kitchens and also inside of a parking garage located in the underground of a supermarket building. The indoor concentrations of NO2 were significantly higher than the concentrations of the external atmosphere and it shows the importance of the sources of internal emissions.

Mental models play an important role in the evolution of an individual's so-called knowledge. Using such representations, students can explain, foresee, and attribute causality to observed phenomena. In the case of Chemistry, the ability to work mentally with models assumes great importance, due to the microscopic component that is characteristic of this science. With the objective of exploring students' ability to work with models, 27 students of the Chemistry Institute of UNESP were asked to describe the mechanisms of dissolution, in water, of NaCl, HCl and HCN, as well as the partial dissolution of I2. Due to difficulties of access to complex descriptors of these processes, each student was asked to explain the phenomena using words and drawings. The results of these investigations were analyzed, and enabled construction of a framework representing the Chemistry students' theoretical training, especially with respect to their most important transferred skill: an ability to model the physical world.

Ammonia is the most common alkaline gas of the atmosphere, being important in the neutralization of various processes that occur in the atmosphere. Its main sources of emission are the decomposition of organic matter and dejections of animals. Ammonia is used by man in diverse activities of production, therefore it is a gas that can contaminate work environments. Measurements of ammonia concentration in some parts of the world have shown great spatial and weather variation. This large variability makes it difficult to estimate the input of reduced nitrogen to different ecosystems from measurements.

An alternative analytical method for nitrogen dioxide (NO2) in atmosphere was developed. The collection of NO2 is performed by a Sep-Pack C-18 cartridge impregnated with 11% (v/v) of triethanolamine plus 3,6 % (v/v) of ethylene glycol plus 25 % (v/v) of acetone combined solution. When the impregnating is used, NO2 is collected with good repeatibility (CV = 3,3 %). The NO2 absorbed in the sampler was stripped from the sorbent with a methanol 5% (v/v) aqueous solution and was determined by colorimetry as nitrite by using the Griess-Saltzman reagent. The detection limit of 1,4 ppb for 60 min sampling at 0,5 L min-1 flow rate was obtained. Preparation and conditioning procedures for TEA-C-18 cartridge, sampling flow rate, absorption capacity and interference of other species are discussed.

Os óxidos de nitrogênio e a amônia são os mais importantes compostos gasosos nitrogenados emitidos para a atmosfera e possuem grande interesse ambiental. Na atmosfera, esses compostos podem sofrer diversas reações resultando em mudanças nas propriedades químicas e físicas da atmosfera. Atividades humanas, principalmente relacionadas com produção de alimentos, energia e uso de fertilizantes têm aumentado as emissões dessas espécies nitrogenadas para o ambiente, causando distúrbios no seu ciclo natural. Com o objetivo de avaliar as variações dos níveis de concentração e inferir sobre os processos de remoção de compostos de nitrogênio da atmosfera na região de Araraquara, foram feitas determinações em paralelo de amônia (NH3) e dióxido de nitrogênio (NO2). Os resultados de concentração mostraram a estreita correlação entre esses compostos na atmosfera, que sugerem diferentes processos de remoção em diferentes épocas do ano.

Nitrogen oxides and ammonia are important nitrogen compounds which are emitted to the atmosphere. They are very important substances in the environment. In the atmosphere, these substances may undergo diverse reactions that result in changes of chemical and physical atmosphere's property. Atmospheric removal mechanisms of nitrogen substances may ocurr either dry deposition or wet deposition. Human activity such as food production, energy and fertilizer have increased the nitrogen emissons to environment, causing disturbances in the natural nitrogen cicle. Parallel determinations of ammonia (NH3) and nitrogen dioxide (NO2) were made to assess variations of concentration and to infer about removal processes theses nitrogen compounds of Araraquara's atmosphere. Results showed the narrow relationship between these substances in the studied atmosphere. This relationship between ammonia and nitrogen dioxide suggested different removal processes at different periods during the year.

A amostragem de amônia no ar é feita usualmente com filtro impregnado com ácido. O ácido ascórbico, quando usado como impregnante, é facilmente oxidado em meio básico e aquoso, gerando uma solução fortemente colorida que inviabiliza a determinação por colorimetria. Este trabalho apresenta um novo procedimento para extração do íon amônio dos filtros de amostragem, transferindo o íon amônio para uma gota de solução contendo ácido sulfúrico 0,1 mol L-1. A amostra do filtro é inicialmente solubilizada com água. A solução é colocada dentro de uma câmara com posterior adição de solução de NaOH 1,5 mol L-1. Com a ajuda de com borbulhamento de nitrogênio, a amônia formada passa para a fase gasosa, sendo finalmente recolhida para uma gota de ácido sulfúrico. A esta gota é adicionado um reagente e o produto determinado colorimetricamente pela reação do indofenol. Além da eliminação de interferentes, o procedimento apresenta a vantagem de fazer uma nova pré-concentração da amônia, possibilitando melhorar o limite de detecção do método de determinação.

Particle NH4+ and gaseous are collected simultaneously by filters impregnated with acid. When ascorbic acid is used, it is easily oxidized in alkaline medium. The resulting solution is dark, making impossible colorimetric measurement. Here we present a new procedure to extract ammonium ion from sampling filters, transferring the N (III) to a droplet of sulfuric acid, 0.1 mol L-1. After sampler collection, each filter is agitated with deionized water. The aqueous solution is transferred to a small chamber where NaOH (1.5 mol L-1 ) is added and nitrogen gas passed. The ammonia changes to the gas phase and is flushed form the aqueous solution. The droplet of sulfuric acid formed at the tip of the glass tube then collects ammonia free of interference. The droplet was analyzed by the indophenol colorimetric technique. Evaluations showed that this procedure could be used at low concentrations and it has the advantage of making a second preconcentration of N (III) , improving the detection limit of the method.