Hydride generation - atomic absorption spectrometry, using sodium tetrahydroborate(III) as a reductant, was used to form arsines selectively from inorganic arsenic(III) and arsenic(V), and dimethylarsinic acid (DMA). The selected reaction media allowed the rapid determination of arsenic(III) alone (citrate buffer 0.4 mol/L, pH 4.4), arsenic(III) + arsenic(V) (HCl 6 mol/L, after pre-reduction with potassium iodide) and arsenic(III) + DMA (acetic acid 0.12 mol/L). Total arsenic could be measured in HCl 6 mol/L, after arsenic(V) and DMA pre-reduction with a potassium iodide and stannous chloride mixture. Interference effects produced by heavy metal ions were also evaluated.

OPTIMIZATION OF THE EXTRACTION OF ANTHOCYANINS PRESENT IN BLACK BEANS AND IMPREGNATION OF THE EXTRACT IN NATURAL POLYMERIC MATRIX FOR USE AS A pH INDICATOR. In this work, a method of extracting natural indicators, anthocyanins, present in black beans was optimized. The best extraction condition was obtained with 50 g of beans and 93 g of water, under agitation at 150 rpm, at a temperature of 40oC for 24 h. The wavelengths of greatest absorption for the indicator in its acidic and basic form were 523 nm and 620 nm respectively and these wavelengths were used to determine the pKa of the indicator. At least three pKa values were observed: 1.9; 7.2 and 10.7. A simplified condition for anthocyanins extraction, the same amount of water, tap water in these case, and beans kept together for 12 h without agitation and temperature control, was also evaluated. Both extracts were impregnated with qualitative filter paper, coffee filter paper and cotton buds and the materials impregnated with the indicator were tested with solutions of HCl, vinegar, NaOH and milk of magnesia. A comparison between the impregnated material and a universal pH indicator paper using buffer solutions pH 4.0, 7.0, 10.0 and 11.2 proved the applicability of the developed material since it presented adequate distinction in its color for the different pH conditions.

This work was performed to evaluate the distribution of metals Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn in the sediment surface in the Itaipu Lake-PR-Brazil. It was also performed to measurement the pH, phosphorus, organic carbon and particle size. In accordance of international criteria of quality of sediment, the results indicate an anthropogenic collaborations since some metals reached an excessive values. The factor of contamination was also used to evaluate the levels of contamination. The levels of Cu and Pb indicate a moderate contamination, so that it's possible to do harm to the balance of the ecosystem studied.

The AVS is defined operationally as acid volatile sulfide, which is a controlling phase on the partition of some metallic species in sediments. A Factorial design was evaluated by means of 16 experiments and using four variables: temperature, extraction time, N2 flow, and volume of the S2- collection solution. The factors that contributed to the efficiency of the process were the extraction time and the N2 flow. Trapping of S2- was efficient in AAB. The S2- was quantified using a potentiometric procedure. Recovery tests for S2- concentrations varying from 1×10-5 to 1×10-4 mol L-1 were in the range from 93 to 116%.

Voltammetry using mercury electrode as working electrode has been employed in the determination of organic and inorganic compounds in several samples. A review on the applications of this analytical tool is present, covering the period of the last ten years. The emphasis of this work is directed to the hanging mercury drop electrode (HMDE), its advantages, disadvantages and applications. Voltammetric measurements are easily carried out, and present low cost. The review discusses that the use of mercury in the measurements can be a limitation due the toxicity of the element. However, nowadays the necessary of volume of Hg in the measurements is very small, and it can be reused. Thus, the correct disposal of the small amount of waste generated can be minimize environmental risks and human health, according to the principles of Green Chemistry.

Abstract The aim of this work was to develop and validate methodology to reduce the digestion time and reagent consumption in the determination of minerals in maize flour. The standard methodology employed in Brazil is that described by AOAC. It consists of the calcination of the sample at high temperatures for a long period of time, making the process expensive and slow. In this work, a wet sample digestion method using HNO3 was employed, heating on a block digester with final dissolution in an ultrasonic bath. The validation tests involved linearity and working range studies, and the determination of the detection and quantification limits, accuracy and precision. The sample digestion time was 1:30 h and the percent recoveries for the metals were 93% for Ca, 98% for Cu, 110% for Fe, 97% for Mg, 101% for Mn and 106% for Zn.

Resumo O carvão ativado pulverizado quando bem embalado e estocado não possui um prazo de validade regulamentado. Em geral, esta validade é determinada de acordo com requisitos estabelecidos pelo próprio fabricante e está diretamente relacionada a uma estimativa de tempo superior ao tempo em que o produto ficará estocado no cliente até a sua utilização. Neste trabalho, avaliou-se a eficiência de carvões ativados de base seca e umectados, relacionando parâmetros de capacidade adsortiva (índice de iodo e umidade) destes materiais com o tempo. Os carvões contendo superfície alcalina não apresentaram variação nos parâmetros avaliados ao longo do tempo de armazenamento, pois não apresentaram significância estatística, uma vez que os valores de F regressão <F crítico e os valores de p > 0,05, tanto para base seca como úmida. Dos carvões com caráter ácido (pH corrigido), apenas um tipo foi mais sensível à adsorção de umidade e iodo ao longo do tempo. A partir da equação de reta oriunda da análise de regressão linear para este carvão, obteve-se a correlação Índice de Iodo = 824 - 0,370 x dias, indicando que o tempo de armazenamento para este material foi igual a 605 dias, garantindo que o valor do índice de iodo seja igual ao valor limite de 600 mg I2.g-1 carvão.

Abstract Activated carbon is commonly used as a material for contaminant-adsorption processes in aqueous systems. However, its use is more restricted to charcoal than to coal, for the most part, in view of the fact of the higher cost (~ 40%) if the mineral is a fossil fuel which needs to be extracted from the earth by mining. For this reason, the peach stone that comes from alimentary industrial tailings can be a good choice for the separation of pollutants from aqueous suspensions and other soluble substances. The purpose of this research was the development of a low-cost filter, using stones to remove atrazine from water. Appraisal and characterization studies were performed along with batch experiments to investigate dosing effects of the activated carbon, atrazine concentration, contact time, and adsorption pH on removal procedures. From the results of the experiment, an excellent removal of the analyte in question was observed under conditions that can be considered as close as possible to the environment, such as pH = 6.5, room temperature and 10 minutes of agitation time, always choosing the best alternative with the lowest cost of energy and time. Batch system application has been recommended as versatile for utilization in seasonal problems such as pesticide contamination.

Trace metal content of three fish species harvested from a tank located in the City of Guarapuava-PR, Brazil were determined by digestion and voltametry. Trace metal content in fish samples were 0.10-1.30 µg/g (muscle) and 0.45-15.90 µg/g (liver) for chromium, 0.35-2.56 µg/g (muscle) and 2.32-34.30 µg/g (liver) for lead. The levels of lead and chromium in fish samples were higher than the recommended legal limits for human consumption. To assess the dietary intake of Cr and Pb by fish, weekly intake was calculated based on average metals contents and weekly consumption of fish and it compared with PTWI (Provisional Tolerable Weekly Intake). The Cr and Pb have achieved up to 25 and 45%, respectively, of PTWI recommended by WHO/FAO.

Infusions of yerba mate obtained at different stages of industrialization were evaluated to determine the bioavailable fraction of Al. Adsorptive Cathodic Stripping Voltammetry using DASA (complexing agent) was applied to determine the labile fraction of Al at pH 5.0 and pH 8.0 for the total fraction of dissolved Al. The results indicate that on average 60% of Al is complexed with organic compounds, minimizing their bioavailability; however, the labile fraction exceeds by up to 4 times the maximum weekly intake recommended by the World Health Organization.