Uso de membranas de Nafion para a construção de sensores ópticos para medidas de pH

The behaviour of Nafion® polymeric membranes containing acid-base dyes, bromothymol blue (BB) and methyl violet (MV), were studied aiming at constructing an optical sensor for pH measurement. BB revealed to be inadequate for developing sensing phases due to the electrostatic repulsion between negative groups of their molecules and the negative charge of the sulfonate group of the Nafion®, which causes leaching of the dye from the membrane. On the other hand, MV showed to be suitable due to the presence of positive groups in its structure. The membrane prepared from a methanolic solution whose Nafion®/dye molar ratio was 20 presented the best analytical properties, changing its color from green to violet in the pH range from 0.6 to 3.0. The membrane can be prepared with good reproducibility, presenting durability of ca. 6 months and response time of 22 s, making possible its use for pH determination in flow analysis systems.

Tecnologia de nanocristais em fármacos

The use of poorly water soluble molecules in pharmaceutical area has grown. Since these molecules exhibit low oral bioavailability, they are not used in intravenous administrations. Therefore, it is necessary to develop their new formulations with the aim to increase their oral bioavailabilities as to enable intravenous applications. One of the few possibilities in achieving this is a nanonization process that can produce crystals smaller than 1 μm by high pressure homogenization and without use of organic solvents. This mini-review describes technical aspects of the nanocrystal production, morphological aspects (polymorphisms), the market relevance of the nanocrystals products that are already in clinical phase or at the market, as well as, perspectives for the near future.

Desidratação osmótica de abacaxi aplicada à tecnologia de métodos combinados

The aim of this research was to optimize osmotic dehydration of pineapple, according to two criteria: maximize water loss and minimize solid gain. The process was made as an application to Combined Methods Technology, in which three preservation factors were combined: water activity, pH and chemical preservatives, all being applied at low levels, in order to get a product resembling non-processed fruit. The experiment was divided into three treatments, being: non-coated pineapple pieces (A), pieces coated with alginate (B) and coated with low-methoxyl pectin (C). Process involved the following main steps: enzymatic inactivation of fruit pieces; in treatments B and C, incorporation of their respective coatings; and osmotic dehydration, in sucrose syrup containing potassium sorbate and citric acid. Optimum conditions, determined from Response Surface Methodology, were the following: dehydration of fruit pieces coated by alginate, at 42-47° C, in sucrose syrup at 66-69° Brix, for 220 to 270 minutes. Results indicated that both coatings significantly affected the mass transfers of the process, reducing solid incorporation and increasing water loss; therefore, increasing weight loss and performance ratio (water loss: solid incorporation) took place. Water activity was not significantly affected by the coatings. The product obtained under optimum conditions was submitted to sensorial evaluation, and presented a good general acceptance. Moulds and yeasts countings indicated good microbiological stability of the product for at least 60 days at 30ºC.

Qualidade de vida e nivel de atividade fisica de funcionarios de empresa de tecnologia da comunicação

Universidade Estadual de Campinas . Faculdade de Educação Física