Mesoporous carbon ceramic SiO2/50 wt % C (SBET=170 m2 g−1), where C is graphite, were prepared by the sol‐gel method. The materials were characterized using N2 sorption isotherms, scanning electron microscopy, and conductivity measurements. The matrix was used as support for the in situ immobilization of Mn(II) phthalocyanine (MnPc) on their surface. XPS was used to determine the Mn/Si atomic ratios of the MnPc‐modified materials. Pressed disk electrodes were prepared with the MnPc‐modified matrix, and tested as an electrochemical sensor for nitrite oxidation. The linear response range, sensitivity, detection limit and quantification limit were 0.79–15.74 µmol L−1, 17.31 µA L µmol−1, 0.02 µmol L−1 and 0.79 µmol L−1, respectively, obtained using cyclic voltammetry. The repeatability of the proposed sensor, evaluated in terms of relative standard deviation was 1.7 % for 10 measurements of a solution of 12.63 µmol L−1 nitrite. The sensor employed to determine nitrite in sausage meat, river and lake water samples showed to be a promising tool for this purpose.

No abstract

No abstract

No abstract

No abstract

We take advantage of polyelectrolyte feature exhibited by natural cashew gum (Anacardium occidentale L.) (CG), found in northeast Brazil, to employ it in the formation of electroactive nanocomposites prepared by layer-by-layer (LbL) technique. We used polyaniline unmodified (PANI) or modified with phosphonic acid (PA), PANI-PA as cationic polyelectrolyte. On the other hand, the CG or polyvinyl sulfonic (PVS) acids were used as anionic polyelectrolytes. The films were prepared with PANI or PANI-PA intercalated with CG or with PVS alternately resulting in four films with different sequences: PANI/CG PANI-PA/CG, PANI/PVS and PANI-PA/PVS, respectively. Analysis by cyclic voltammetry (CV) of the films showed that the presence of gum increases the stability of the films in acidic medium. The performance of the modified electrode of PANI-PA/CG was evaluated in electro analytical determination of dopamine (DA). The tests showed great sensitivity of the film for this analyte that was detected at 10−5 mol L−1.

Avaliação da água, principalmente daquela destinada ao consumo humano, é de fundamental importância, já que esta é um dos principais veículos de doenças. A desconfiança sobre a água proveniente do sistema público de abastecimento é um dos principais fatores que levam à utilização de fontes alternativas, como a água envasada, no entendimento de que essa fonte é segura. Com isso há um aumento do consumo de água mineral, principalmente em garrafões de 20 litros, substituindo a água dos sistemas de abastecimento público para consumo nas residências, escritórios, empresas e escolas. Portanto, o presente estudo visa contribuir para ampliar o conhecimento a respeito da qualidade da água mineral das principais marcas comercializadas em embalagens retornáveis de 20 litros no município Picos-PI. A partir das análises físico-químicas

No abstract