Avaliação das condições de precipitação do azul da Prússia sobre pó de grafite visando o desenvolvimento de eletrodos de pasta de carbono para a quantificação de nitrito

An amperometric FIA method for nitrite quantification based on nitrite electroreduction and employing a carbon paste electrode (CPE) chemically modified with iron hexacyanoferrate (HCF) as an amperometric detector was developed. The influence of experimental conditions on the preparation of the electrode materials was evaluated and the materials obtained in each study were used for the development of modified electrodes. The electrochemical sensors were prepared by a fast, simple, and inexpensive procedure, and the long-term performance of the electrodes were quite satisfactory as the stability was maintained over one year. HCF was an effective redox mediator for nitrite electroreduction in acidic media, allowing nitrite detection at +0.2 V vs. Ag/AgClsat, which is a potential free of possible interfering species that are normally present in food and water samples. The electrochemical cell used in the FIA system was similar to a batch injection analysis cell, enabling recirculation of the carrier solution. This is an attractive feature because it allows the use of a high flow rate (6 mL min-1) leading to high sensitivity and analysis speed, while keeping reagent consumption low. The proposed method had a detection limit of 9 μmol L-1 and was successfully employed for nitrite quantification in spiked water and sausage samples. The obtained results were in good agreement with those provided by the spectrophotometric official method. At a 95 % confidence level it was not observed statistical differences neither in nitrite content nor in the precision provided by both methods. The experimental conditions for the synthesis of HCF were optimized and the best electrode material was prepared by mixing FeCl3, K4[Fe(CN)6] and carbon powder subjected to an acid and thermal treatment (400 ºC), followed by ultrasonic agitation at 4 °C. This material was used to construct an electrode with improved analytical performance to reduce nitrite, which presented greater stability compared to HCF film electrodeposited on the EPC, showing that the preparation procedure of the electrode material is an effective strategy for the development of HCF modified electrodes.

A busca por uma política nacional dos biocombustíveis como tutela do direito fundamental ao meio ambiente : acautelamento e avaliação de riscos

The work is to demonstrate the scope of modern-day major regulatory provisions and the policies implemented to adoption of biofuels in the national energy matrix. The adoption of biofuels as an alternative to fossil fuels, is based on the realization of the fundamental right to an ecologically balanced environment mitigating hazards and environmental hazards arising from a postmodern society. However, the change in the Brazilian energy matrix observe the precepts of certain environmental principles to essentially environmental preservation The proposed Environmental rule of law is founded on the realization of the right (duty) key to an ecologically balanced environment for sustainable development. Thus, it is up to the State, in addition to considering the dangers and risks fruits of government decisions, present the possible instruments to mitigate the irreversible environmental damage to the environment. The management of environmental risks present in the ideals of an Environmental rule of law, plays an important role in the preservation and economic development, using, therefore, of acautelatórios legal instruments, such as environmental licensing and the ecological-economic zoning, measures adopted in the light of the principles of precaution and preservation. The adoption of research in the environmental field, improvement and development of environmental technology, building a system to observe ecological changes, imposition of environmental policy objectives to be achieved in the medium and long term and systematization of organizations plan a protection policy environmental, are essential measures to control possible environmental risks and damage guided by the aforementioned environmental principles. Thus, it will be used the inductive method of approach, starting from the analysis of the new perspective of Environmental rule of law and the implementation of biofuels in the context of a post-modern society, marked by uncertainty and the risk of damage, from the study of the principles of caution, maintaining and cautionary measures in mitigating the hazards and potential risks.