In this study a new method for determination of cadmium in alcohol fuel using Moringa oleifera seeds as a biosorbent in an on-line preconcentration system coupled to flame atomic absorption spectrometry (FAAS) was developed. Flow and chemical variables of the proposed system were optimized through multivariate designs. The limit of detection for cadmium was 5.50microg L(-1) and the precision was below 2.3% (35.0microg L(-1), n=9). The analytical curve was linear from 5 to 150microg L(-1), with a correlation coefficient of 0.9993. The developed method was successfully applied to spiked alcohol fuel, and accuracy was assessed through recovery tests, with recovery ranging from 97.50 to 100%.

No abstract

No abstract

In this study, the experimental extraction conditions on applying headspace solid-phase microextraction and cold fiber headspace solid-phase microextraction (CF-HS-SPME) procedures to samples of six medicinal herbs commonly found in southern Brazil were optimized. The optimized conditions for headspace solid-phase microextraction were found to be an extraction temperature of 60°C and extraction time of 40 min. For CF-HS-SPME, the corresponding values were 60°C and 15 min. In the case of the coating temperature for the CF-HS-SPME system, two approaches were investigated: (i) Temperature of 5°C applied during the whole extraction procedure; and (ii) the use of two fiber temperatures in the same extraction procedure with the aim of extracting the volatile and semivolatile compounds, the ideal condition being 60°C for the first 7.5 min and 5°C for the final 7.5 min. The three extraction procedures were compared. The CF-HS-SPME procedure had good performance only for the more volatile compounds whereas the strategy using two coating temperatures in the same procedure showed good performance for all compounds studied. It was also possible to determine the profile for the volatile fraction of each herb studied applying this technique followed by GC-MS.

No abstract

Neste estudo foi desenvolvida uma metodologia analítica para determinação de 2,4-dinitrofenol (2,4-DNP) em amostras de águas de chuva de regiões de Santa Catarina utilizando a voltametria de onda quadrada (VOQ) e de forma ex situ. O estudo envolveu a aplicabilidade de utilizar o eletrodo de carbono vítreo modificado com filme de bismuto. A formação do filme de bismuto foi otimizada por voltametria cíclica e em seguida, estudos de pH e eletrólito de suporte foram investigados para a redução do 2,4-DNP. Os parâmetros analíticos que afetam a sensibilidade da VOQ foram otimizados. Na sequência, as figuras analíticas de mérito foram obtidas: faixa linear de trabalho de 3,2 x 10-7 – 4,6 x 10-6 mol L-1, coeficiente de correlação de 0,996, RSD% = 17,5 (1,3 x 10-6 mol L-1, n = 6), 11,7 (2,5 x 10-6 mol L-1, n = 6) e 6,4 ( 4,5 x 10-6 mol L-1, n = 6), limite de detecção de 1,2 x 10-7 mol L-1. E, finalmente estudos de recuperação foram realizados para avaliar a exatidão da metodologia. Valores obtidos ficaram entre 84-112% (2,5 x 10-6 mol L-1) e 89 – 113% (4,5 x 10-6 mol L-1).

IntroduçãoO níquel é um elemento natural muito abundante no meio ambiente e pode ser combinado com outros metais, tais como ferro, cobre, cromo e zinco, para formar ligas [1]. A importância da determinação de íons de elementos de transição, tais como Ni(II), em amostras ambientais, é bastante enfatizada devido a sérios riscos que esses elementos causam ao sistema biológico. As principais fontes de Ni(II) em sistemas aquáticos são provenientes da dissolução das rochas e solos, ciclos biológicos, e especialmente de processos industriais [2]. Sabe-se que a inalação de compostos que Esses metais encontram-se, em geral, em concentrações-traço e por isso é necessário o desenvolvimento de métodos analíticos que possibilitem suas determinações quantitativas de acordo com os crescentes níveis de exigência das organizações governamentais.A espectrometria de absorção atômica em chama (F AAS) é uma das técnicas mais uti-

A new method for Ag determination in water samples using solid phase extraction (SPE) coupled to a flow injection system and flame atomic absorption spectrometry was developed. The sorbent used for Ag preconcentration and extraction was the termite digestion product. Flow and chemical variables of the system were optimized through a multivariate procedure. The factors selected were adsorbent mass, buffer type and concentration, sample pH, and sample flow rate. The detection limit and precision were 3.4 μg L−1 and 3.8% (n = 6, 15 μg L−1), respectively. The enrichment factor and the linear working range were, respectively, 21 and 10–50 μg L−1. Results for recovery tests using different water samples were between 96 and 107%. The proposed methodology was applied with success for the determination of Ag in water used to wash clothes impregnated with silver nanoparticles, supplied by a factory located in Santa Catarina, Brazil.