Decomposição térmica de espumas de poliuretano para fabricação de vitrocerâmica celular de Li2O-ZrO2-SiO2-Al2O3 (LZSA)

Characterization of the thermal decomposition of polyurethane (PUR) foams was performed by Fourier-transformed infrared (FT-IR) spectroscopy and thermogravimetric analysis (TGA). Three main weight loss paths were observed by TGA, the residue being lower than 3 wt.% for 3 different PUR foams analyzed. FT-IR spectra indicated CO2, CO, NH3 and isocyanides as main decomposition products. PUR foams of different cell sizes were immersed in a slurry of the parent glass ceramic of composition Li2O-ZrO2-SiO2-Al 2O3 (LZSA) and submitted to heat treatment. The LZSA cellular glass ceramics obtained after sintering and crystallization resembled the original morphology of the PUR foams.

Caracterização física, química e ecotoxicológica de efluente da indústria de fabricação de explosivos

The production and use of nitroaromatic explosives have resulted in their dissemination into the environment, where their presence in waterways and soil represents an ecological and health hazard. The hazardous characteristics of these compounds need to be carefully studied, so that the impact of their discharge on the environment can be better evaluated. This work presents the characterization of wastewater from Brazilian TNT industry using as analytical techniques mass spectroscopy, chromatography, toxicity assays and other physico-chemical analyses.

Uso da pressão gerada por uma coluna de água para controle da vazão em sistemas de análises em fluxo

This work presents a new approach to control the flow rate in hydrodynamic flow experiments. The combination of air pressure generated by an aquarium air pump and the pressure generated by a water column were used for this purpose. This device supports a stable flow rate without pulsation for a long period of time. Furthermore, the flow rate can be easily controlled at various values in one or more streams. The performance of this approach was investigated using Fe(CN)6(4-) solutions in flowing systems using amperometric and voltammetric detection in wall-jet configuration. The results showed that the performance of the proposed device was better than a commercial peristaltic pump. It suggests that this approach can be used successfully in flow analysis systems.

Microssistemas de análises químicas: introdução, tecnologias de fabricação, instrumentação e aplicações

The amazing world of micro total analysis systems has provided a true revolution in analytical chemistry in recent years. The application of the microfluidic devices for chemical and biochemical processing has attracted considerable interest due to its advantages such as reduced sample and reagent consumption, processing time, energy, waste, cost, and portability. The aim of the present report is to disseminate the state of the art related to the miniaturization science in Analytical Chemistry. Historical progress, microfabrication technologies, required instrumentation and applications of the mTAS are presented in the current article, with special attention to the Brazilian contributions.

Construção de um sistema simples e compacto de recirculação d'água sob pressão para trompa d'água

Vacuum pumps are very useful in physical, chemical and biological experiments. In this communication it is described the design of a compact and low cost water recirculating system employing a water-jet aspirator pump as the vacuum source. The system requires only a water pump, water-jet aspirator pump, commercial PVC water tubes and a drain connection.

Heterogeneidade de álcoois secundários em aguardentes brasileiras de diversas origens e processos de fabricação

Secondary alcohol concentrations in sugar cane spirits from different origins were determined by gas chromatography. A great variation in the concentration of the secondary alcohols was found in these spirits. Of the 33 brands analyzed, 8 of them were found to be out of conformity with the legislation. Sec butanol, for which the maximum allowed concentration level is 100 mg.L-1 in absolute ethanol, was found within a concentration range between 5 mg.L-1, the limit of quantitation (LQ) and 408 mg.L-1 in absolute ethanol. Sugar cane samples from Salinas, MG, were the only ones that exhibited self similarity because of the low concentrations of n-butanol and n-amylic alcohol (< limit of detection LD).

Métodos para fabricação de microeletrodos visando a detecção em microambientes

Analysis at microenvironments, like single cells or in minute volumes (nL), is an area of great interest for analytical and biological sciences. Measurements at these experimental conditions demand analytical tools (microelectrodes) capable of monitoring with rapid response, good resolution and minimal perturbation of the system. The major drawbacks in producing these microscopic electrodes have been largely overcome, principally due to the development of new fabrication methods. In this review, these procedures are described with emphasis to those devoted to the construction of microelectrodes for application in microenvironments. Examples of our efforts to use these devices as effective electrochemical sensors are also addressed.

Nanoemulsões óleo de laranja/água preparadas em homogeneizador de alta pressão

The objective of this work was to use the high-pressure homogenizer (HPH) to prepare stable oil/water nanoemulsions presenting narrow particle size distribution. The dispersions were prepared using nonionic surfactants based on ethoxylated ether. The size and distribution of the droplets formed, along with their stability, were determined in a Zetasizer Nano ZS particle size analyzer. The stability and the droplet size distribution in these systems do not present the significant differences with the increase of the processing pressure in the HPH). The processing time can promote the biggest dispersion in the size of particles, thus reducing its stability.

Reator de UV-Ozônio com lâmpada a vapor de mercúrio a alta pressão modificada para tratamento superficial de óxidos transparentes condutivos utilizados em dispositivos poliméricos eletroluminescentes

An UV-Ozone reactor was developed with an ignition tube extracted into HID mercury lamp used to irradiation on zinc oxide (ZnO) and fluorinated tin oxide (FTO) films for PLEDs devices. Different exposures times were used. In contact angle measurements revealed better results for ZnO and FTO by 15 and 5 min, respectively. In Diffuse Reflectance Infra-red Fourier Transformed (DRIFT) spectroscopy allowed the observation of water, hydrocarbon and carbon dioxide adsorbed on the untreated TCO surfaces. After the UV-Ozone treatment the contaminants were significantly reduced or eliminated and the PLEDs devices decreased threshold voltages in comparison with respectively untreated TCOs.

Avaliação de métodos de extração para a determinação de cromo e níquel em formulações farmacêuticas e em matérias-primas usadas na fabricação de medicamentos à base de cefalexina e ciprofloxacino

This paper reports the evaluation of extraction strategies for the treatment of medicine samples to determine chromium and nickel by GFAAS. Different approaches for extraction were evaluated and the most efficient involved magnetic stirring. The metals were quantitatively extracted by stirring 0.20 g samples with 25 mL of 2.0 mol L-1 HCl solution for 60 min. The developed method was successfully applied for the determination of Cr and Ni in tablets containing antibiotics and raw materials, with cephalexin and ciprofloxacin as active ingredients.

Equipamento de baixo custo para extração em fase sólida em amostras aquosas de grande volume utilizando pressão positiva de N

Extraction/concentration is a crucial step for the analysis of organic compounds at trace level concentrations and dispersed in complex matrices. Solid-phase extraction (SPE) is one of the techniques used for this purpose. In this work, a low cost apparatus for SPE was developed that uses nitrogen under positive pressure and ensures the maintenance of the sample flow, while also allows the simultaneous extraction of different samples without cross-contamination and sample contact with plastic materials. For the system set up, easily accessible materials were used such as hypodermic needles, stainless steel tubes, rubber stoppers, and 3-way valves from serum delivery apparatus.

COMPARAÇÃO E CONSTRUÇÃO DE REATORES DE "MILD" E "HARD ANODISATION" PARA FABRICAÇÃO DE ALUMINA ANÓDICA POROSA

The mild anodization (MA) reactor is exemplified for its operational simplicity and its excellent control over the experimental parameters that are involved in the anodization process. This method provides porous anodic alumina films with a regular cell-arrangement structure. This offers a better cost-benefit ratio than the other equipment configurations that are used to fabricate nanoporous structures (i.e., ion beam lithography). Conversely, the hard anodization (HA) reactor produces oxides at a rate that is 25 to 35 times faster than the MA reactor. The produced oxides also have greater layer thicknesses and interpore distance, and with a uniform nanopore spatial order (> 1000). In contrast to MA reactors, the construction of an HA reactor requires special components to maintain anodisation at a high potential regime. Herein, we describe and compare both reactors from a technical viewpoint.

Colonização de raízes de plantas daninhas cultivadas in vitro e em vasos por Ralstonia solanacearum, biovares 1, 2 e 3

No presente trabalho, a colonização de raízes de espécies de plantas daninhas por estirpes das biovares 1, 2 e 3 de Ralstonia solanacearum foi avaliada in vitro e em casa de vegetação. Na condição in vitro, sementes foram submetidas à quebra de dormência, desinfestadas e semeadas em meio de cultura Murashige & Skoog (MS) modificado. A bactéria foi inoculada, colocando uma porção da massa no meio MS ao lado das plântulas. A colonização de raízes foi avaliada visualmente de acordo com a concentração de bactérias ao redor e na extensão das raízes e comparada a uma escala diagramática que variou de 1 a 4. Foi analisada a área abaixo da curva de colonização de raízes. Em casa de vegetação, populações de seis variantes das mesmas biovares foram quantificadas a partir de raízes de plantas daninhas. A bactéria foi inoculada nas raízes sem ferimentos, vertendo-se 100 ml da suspensão bacteriana na concentração de aproximadamente 10(8) ufc/ml por vaso. A avaliação foi feita aos 35 dias após a inoculação através do plaqueamento dos extratos diluídos das raízes e contagem posterior das colônias. Foram observados diferentes sintomas e níveis de colonização de raízes pela bactéria nas espécies de plantas estudadas. Os dois métodos permitiram o estudo da colonização de raízes com resultados análogos, sugerindo que ambos permitem obter resultados similares. Entretanto, a técnica in vitro é promissora como método auxiliar para a avaliação da colonização radicular de grande número de espécies botânicas por diferentes isolados de R. solanacearum.

Pressão interna e refração molar dos sistemas dimetilsulfóxido + tiofeno, dimetilsulfóxido + piridina a 298,15K

Pressão interna, volume livre, refração molar e propriedades termodinâmicas de excesso de misturas líquidas binárias de dimetil sulfóxido + tiofeno e dimetil sulfóxido + piridina a 298.15K foram calculadas a partir de medidas experimentais de densidades, tensão superficial e índice de refração. A relação entre a pressão interna, volume molar de excesso, refração molar, e a interação molecular dos sistemas binários é examinada.

Influência de idade e da posição radial nas dimensões das fibras e dos vasos da madeira de Eucalyptus grandis Hill ex. Maiden

Objetivou-se neste trabalho avaliar a variação das dimensões das fibras e dos vasos da madeira de Eucalyptus grandis com quatro diferentes idades (10, 14, 20 e 25 anos), proveniente de talhões comerciais. A amostragem do material na árvore foi feita através da coleta de três discos, retirados da base e das extremidades das duas primeiras toras, ambas com o comprimento comercial de 3 m. De cada disco, retiraram-se cinco amostras, de dimensões 1,0 x 1,0 x 1,0 cm, tomadas de pontos eqüidistantes, correspondentes a 0; 25; 50; 75; e 100% da seção, no sentido radial medula-casca, fazendo-se a medição das fibras e dos vasos. Verificou-se, em todos os parâmetros, o efeito da idade e da variação radial, no sentido medula-casca, à exceção da largura e do diâmetro do lume das fibras; todos os demais parâmetros apresentaram correlação positiva.