The role of the "tape tea" as a low cost abuse drug is evaluated, by searching for possible inorganic and organic compounds after its preparation. Two energy sources are evaluated (conventional and microwave heating) for preparing the "tape tea" using new or used cassette (K7) or video home system (VHS) tapes. After optimizing all the inductively coupled plasma mass spectrometry (ICP-MS) conditions, the remarkable presence of Mn and Co, as well as Cr and Ni, at concentrations higher than 5 times those allowed for drinking water, makes the use of the "tape tea" plausible as a non-cost abuse drug due to some possible neurotoxic effects. Regarding the Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) analysis, no evidence of any organic compound related to neurological effects was found.

Antioxidant systems, Fe, Cu, Zn, Mn and Ni levels and proteomics in soybean seeds of different performance in field were assessed. These results were correlated with the in vitro tests required by regulatory organisms, and the actual behavior in field. Basal superoxide content, superoxide dismutase (SOD) activity (20-80 U mg-1 protein) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity (4.6-7.0 mg antioxidant per g dry seed) permitted to study the oxidative stress of seeds. Essential metal levels were in accordance to previous reports, with the exception of Zn that was higher in some batches of good in vitro quality, but poor performance in field. Proteomic profile showed no differences between batches. Two of the studied parameters (basal superoxide content and Zn level) contribute to a better assessment of the health state of the seeds and predict a possible poor performance in field.

Cloud point extraction was employed for the separation and preconcentration of cadmium and lead prior to the determination by thermospray flame atomic absorption spectrometry. Di-2- pyridyl ketone salicyloylhydrazone (DPKSH) was used as complexing agent and the cadmium and lead complexes were extracted from the aqueous phase by the Triton X-114 surfactant. The variables associated with the preconcentration (pH as well as DPKSH, surfactant and electrolyte concentration) were optimized by using a full factorial design with two levels, four variables and a central composite. Under the optimized conditions, a sample volume of 100 µL was introduced into a hot Ti tube at a flow rate of 0.6 mL min-1 and the integrated absorbance was measured. Calibration curves were obtained with linear ranges of 0.075-2.0 µg L−1 (Cd) and 2.5-100 µg L−1 (Pb). The detection limits of 0.04 µg L−1 (Cd) and 1.3 µg L−1 (Pb) (99.7% confidence level) were obtained. The proposed method was applied to hemodialysis solutions and water samples. The accuracy of the method was evaluated by analyzing a certified reference material (NIST CRM 1643e) and the results were in agreement with the certified values at a 95% confidence level according to t-test.

Apresenta-se um procedimento para extração de Ca, K e Mg de amostras de cultivo in vitro de plantas, comparando-se culturas de calo com diferentes potenciais embriogênicos de Citrus sinensis e Citrus limonia, com o emprego de energia ultra-som. Foram investigados os parâmetros relacionados com a extração de metais, tais como tipo de amostragem do material, concentração do ácido e tempo de sonicação. Visando a comprovação da exatidão, o procedimento de extração ultra-sônica foi comparado com o de digestão ácida assistida por microondas, e não foram observadas diferenças estatísticas significativas em um nível de confiança de 95%. Com este procedimento de extração simples e preciso, foi possível estabelecer diferenças nas concentrações de Ca, K e Mg durante a formação/desenvolvimento dos embriões de Citrus, bem como entre as culturas (embriogênicas e não-embriogênicas). Finalmente, a extração ultra-sônica demonstrou-se uma excelente alternativa para menor manipulação das amostras e redução de custos operacionais.

An ultrasound extraction procedure for Ca, K and Mg from in vitro plant cultures is proposed, comparing cultures of different embryogenic levels of Citrus sinensis and Citrus limonia, employing ultrasound energy. Parameters related to metals extraction, such as plant material sampling, acid concentration and sonication time were investigated. For accuracy check, the proposed ultrasound extraction procedure was compared with a microwave-assisted digestion procedure and no differences in the results were verified at 95% of the confidence level. With this simple and accurate extraction procedure, it was possible to determine differences in Ca, K and Mg concentrations during Citrus embryo formation/development and between cultures (embryogenic and non-embryogenic). Finally, the ultrasound extraction method demonstrated to be an excellent alternative for handless sampling and operational costs.

Amostras de vermicomposto (material húmico) foram submetidas à caracterização por espectroscopia de infravermelho, difractometria de raios-X, termogravimetria, microscopia eletrônica, entre outras; adicionalmente, foi determinada a capacidade de troca catiônica (CTC). Empregou-se planejamento fatorial para estudar os mecanismos de interação da espécie Cd2+ com os sítios adsortivos do vermicomposto e, posteriormente, foi avaliada a máxima capacidade adsortiva de cádmio empregando isoterma de Langmuir. A caracterização revelou que o vermicomposto exibe CTC tão elevada quanto 72,9 meq por 100 g, grande área superficial (substância porosa), grupos quelantes e máxima capacidade adsortiva para Cd (38,6 mg g-1) em pH 5,0. Esta potencialidade foi explorada em análises de amostras sintéticas e reais (água mineral) apresentando concentrações de cádmio próximas a 5 mig L-1 e requerendo etapas de pré-concentração. Um fator de enriquecimento de 100 foi obtido.

Vermicompost (humic material) samples were submitted to characterization by infrared spectroscopy, X-ray diffractometry, thermogravimetric analysis, electron microscopy etc. In addition, its cation exchange capacity (CEC) was determined. Factorial experiments were designed in order to elucidate the interaction mechanisms between Cd2+ and the adsorptive sites of vermicompost. The maximum adsorptive capacity for cadmium was evaluated by a Langmuir isotherm. The characterization revealed that vermicompost exhibits high CEC values (ca. 72.9 meq per 100 g), high surface area (porous material), chelating groups and a maximum adsorptive capacity for Cd (38.6 mg g-1) at pH 5.0. This potential application was exploited in the analysis of synthetic and real (mineral water) samples with Cd concentrations of ca 5 mug L-1, requiring a preconcentration step. An enrichment factor of 100 was attained.

The aim of this work was to propose two different didactic experiments, which can be used in practical classes of analytical chemistry courses. More flexible experiments related to the theme, giving some options to the instructor are proposed. In this way, the Experiment 1 was divided in two parts. In the first one, the visualization of two distinct phases separation is emphasized: the rich and the poor phases in surfactant. In the second part, the metal pre-concentration (Co as example) is emphasized. The Experiment 2 has three different parts. In the first one, the complex formation is pointed out, in the second one, the pH influence is shown and in the last one, the influence of the complexation time is demonstrated.

This work describes a factorial design for the optimization of pyrolysis and atomization temperatures in ETAAS. As examples, Cd and Pb were determined using lower pyrolysis and atomization temperatures and Al and Mo with higher pyrolysis and atomization temperatures. Good results were obtained for Cd employing Rh (m o = 1.4 pg) as a permanent modifier with pyrolysis and atomization temperatures of 640 and 1500 °C, respectively. For Zr, W or Zr+W, the Cd pyrolysis and atomization temperatures were 500 and 1500 °C, respectively, with m o = 1.4 pg using Zr or W and 1.5 pg using Zr+W. The best results for Pb were those using Rh, Zr, W and Zr+Rh, obtaining characteristic masses of 42, 37, 34 and 36 pg, respectively. Pyrolysis and atomization temperatures of 910 and 1850 °C, respectively, were achieved for this metal. For Al, the best results were obtained when Zr or Zr+W were used. Mo was also tested as a possible permanent modifier for Al, but the results were not satisfactory. The results obtained for Mo without modifier were similar to those with conventional modifiers (Mg or Pd+Mg) and the results obtained using permanent chemical modifiers were not satisfactory. In all situations, the experiments were performed faster than those using the univariate procedure.

Foi desenvolvido um procedimento experimental para a análise direta de sedimento. Com o emprego deste procedimento, foram determinados cobre, zinco e chumbo, e foram conseguidas recuperações quantitativas para esses metais com baixo custo e manipulação mínima das amostras. Foram investigadas a influência da concentração do ácido nítrico no preparo da suspensão, bem como o tamanho de partícula do sedimento. As suspensões do sedimento foram tratadas com ácido nítrico 6,0 mol L-1 e cloreto de amônio 2% (m/v), e sonicadas por 15 minutos em um banho de ultra-som antes da quantificação por espectrometria de absorção atômica com chama. Empregando essas condições, a porcentagem de recuperação para cobre, zinco e chumbo foram 96,4 ± 4,9; 97,0 ± 4,0 e 99,7 ± 4,0, respectivamente, empregando-se um material certificado de referência.

An experimental procedure for direct sediment analysis was developed. Using this procedure, copper, zinc and lead were determined and quantitative recoveries for these metals were accomplished at a low cost and with minimal sample manipulation. The influence of the nitric acid concentration on the slurry preparation, as well as the sediment particle size was investigated. Sediment slurries were treated with 6.0 mol L-1 nitric acid and 2% (m/v) ammonium chloride, and sonicated for 15 minutes in an ultrasonic bath before quantification by flame atomic absorption spectrometry. Using these conditions for a certified reference material, the percentage of recovery for copper, zinc and lead were 96.4 ± 4.9, 97.0 ± 4.0 and 99.7 ± 4.0, respectively.

Com o emprego de um método simples e rápido, são propostas algumas condições de otimização para a obtenção de máxima intensidade de cavitação em banhos de ultra-som. Os parâmetros estudados foram: volume de água dentro do banho, temperatura, concentração de detergente, posição vertical e horizontal dos tubos no banho, número de tubos dentro do banho, tempo de sonicação e substituição da água do banho. Os resultados obtidos para os banhos de ultra-som estudados (Neytech e Cole-Parmer) permitiram estabelecer as seguintes condições para máxima intensidade de cavitação: 1 L de água à temperatura ambiente; 0,2 % (v/v) de detergente; posição central e ao fundo do banho. Somente 1 tubo deve ser usado por vez dentro do banho durante a aplicação do ultra-som. A intensidade de cavitação foi linear com o tempo de sonicação até 10 minutos e a substituição de água durante a sonicação melhorou a reprodutibilidade. Esse sistema de troca contínua de água permite a sonicação de até 6 amostras consecutivamente sem mudanças no volume total de água.

Optimisation conditions for obtaining maximum cavitation intensity in ultrasonic baths are proposed using a simple and fast method. Parameters such as water volume, temperature, detergent concentration, horizontal and vertical positions, number of tubes in the bath, sonication time and bath water substitution were studied. The results obtained for both baths studied (Neytech and Cole-Parmer) lead to the following conditions for maximum cavitation intensity: 1 L of water at room temperature, 0.2 % (v/v) of detergent, central position on the bottom of the tank. Only one tube at a time should be used inside the bath during the ultrasound application. The cavitation intensity was linear with the sonication time up to 10 minutes and the water substitution during the sonication improved reproducibility. This system using continuous water change makes possible the sonication of 6 consecutive samples, without changes in the water volume.

A técnica de amostragem de suspensão aliada à espectrometria de absorção atômica com chama foi empregada para a determinação direta de Cu, Fe, Mn e Zn em matrizes de Krill antártico. O efeito dos parâmetros instrumentais e o preparo das suspensões foram estudados em função do sinal analítico. Para a determinação de Cu, Fe e Zn, as amostras foram suspensas em uma solução de HNO3 2,0 mol L-1 e para a determinação de Mn, o krill foi suspenso em uma solução de HNO3 4,0 mol L-1. A precisão entre as replicas foi melhor que 5 %. A metodologia foi aplicada para a determi-nação direta de Cu, Fe, Mn e Zn em amostras de krill antártico, usando padrões aquosos no preparo das curvas analíticas. Os resultados obtidos estão concordantes com os encontrados na determinação por FAAS e ICP-AES, depois da digestão das amostras em um forno de microondas. Os limites de detecção foram 4,5; 1,0; 4,9 e 8,4 mig L-1 para Cu, Zn, Mn e Fe, respectivamente.

Slurry sampling in combination with flame atomic absorption spectrometry was employed for the direct determination of four essential trace elements, namely Cu, Fe, Mn and Zn in Antarctic krill. The effect of instrumental operating conditions and slurry sampling preparation on the analytical signal was investigated. For the determination of Cu, Fe and Zn, samples were suspended in a solution containing 2 mol L-1 HNO3. In the case of Mn, 4 mol L-1 HNO3 was necessary for the preparation of the slurry. The precision between sample replicates was better than 5%. The method was applied to the direct determination of Cu, Fe, Mn and Zn in Antarctic krill samples using aqueous reference solutions to prepare the calibration curves. The results obtained were in good agreement with those achieved by FAAS and ICP-AES after microwave-assisted wet digestion of the krill samples. The detection limits were 4.5, 1.0, 4.9 and 8.4 mug L-1 for Cu, Zn, Mn and Fe, respectively.