A method for the preconcentration and determination of cobalt in human urine samples was developed. The online preconcentration and determination were attained using inductively coupled plasma atomic emission spectromety (ICP-AES) coupled to a flow injection (FI) method. Cobalt was retained on an Amberlite XAD-7 resin as cobalt-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol complex at pH 9.5. Cobalt was removed from the microcolumn with perchloric acid. A sensitivity enhancement factor of 90 was obtained with respect to cobalt determination by ICP-AES without preconcentration. The value of detection limit for the preconcentration method proposed was 25 ng/L. The precision for 10 replicate determinations at the 5 mg/L (mean +/- SD, 5.1 +/- 0.14) Co level was 2.7% relative standard deviation, calculated from the peak heights obtained. The calibration graph preconcentration method for cobalt was linear with a correlation coefficient of 0.9994 from approximately 0.25 mg/L up to at least 100 mg/L. The method was successfully applied to the determination of cobalt in human urine samples.
Wind turbines have been widely used, and one of the main reasons is the low environmental impact caused by these technologies. However, for the Amazon Region the design of small turbines is still challenging, because most of the turbines available present low capacity factor. Hence, this work deals with a new methodology to assess the energy production of a small wind turbine with high capacity factor, specially designed for the Brazilian Amazon Region. The blade element theory was employed into the dynamic equation of the powertrain, in order to establish a steady-state model. Experimental data were obtained using a bench setup developed to test small electric generators. Data for the shaft rotation speed of a synchronous generator with permanent magnets were measured. The interception between mechanical power and generator curves was also proposed to calculate the operating condition of the turbine. All simulations were made in an autonomous system, using a height of 15 m above ground level in the city of Salinópolis on the coastal area of the state of Pará, Brazil. The capacity factor verified was higher than those of two wind turbines of 1 kW available on the market. This result shows that the use of a turbine adapted to low average wind speeds can contribute to a better use of the available wind potential in the region.
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