Ana Paula Ruas de Souza

The use of a gold disc microelectrode for the determination of copper in human sweat

A novel approach of using a gold disc microelectrode to analyze sweat samples for copper ions by anodic square wave stripping voltammetry (SW stripping voltammetry) is described. Sweat was collected from the lower back of four subjects after physical exercise and the sample volume required for the determinations was 100 μL. Under the optimized conditions, the calibration plot was linear over the range 1-100 μmol L(-1) Cu(II) with a limit of detection of 0.25 μmol L(-1). The precision was evaluated by carrying out five replicate measurements in a 1 μmol L(-1) Cu(II) solution and the standard deviation was found to be 1.5%. Measurements were performed by inserting the microelectrode into sweat drops and Cu(II) concentrations in the analyzed samples ranged from 0.9 to 28 μmol L(-1). Values obtained by the proposed voltammetric method agreed well with those found using graphite furnace atomic absorption spectroscopy (GFAAS).

On site stripping voltammetric determination of Zn(II), Cd(II) and Pb(II) in water samples of the Cananéia-Iguape Estuarine-Lagoon complex in São Paulo state, Brazil

Estuarine systems play an important role in the retention of toxic trace elements owing to the affinity of these elements with particles dissolved in water. This work presents the use of a voltammetric sensor to monitor heavy metal (Zn (II), Cd(II) and Pb (II)) concentrations in the Cananeia-Iguape Estuarine-Lagoon region (Sao Paulo State, Brazil). Lower concentrations were found in the Southern estuarine system (Cananeia City) and increased concentrations observed in the Northern sector (Iguape City) were promoted by anthropogenic activities, with particular influence from the historical introduction of mining wastes and inputs from agricultural, industrial and domestic effluents. The proposed method is reliable, inexpensive and fast, can simultaneously provide information on the concentration of these metallic ions and can be easily used for field measurements aboard oceanographic ships.

Gold random microarrays: design, characterization and amperometric determination of ciclopirox olamine in pharmaceutical products

In this work, a disposable gold random microarray (GRM) sensor was developed and applied for the determination of ciclopirox olamine in 0.10 mol L−1 Britton Robinson buffer (pH 5.0). The GRM was fabricated by the deposition of two toner pattern masks, the first mask delimiting the disc area and the second one (with 90% of toner) defining the microarrays. Following the optimization of the experimental parameters, the proposed sensor presented excellent analytical properties for the amperometric detection of ciclopirox olamine at +0.85 V vs. Ag/AgCl(KClsat). The usefulness of the GRM sensor was confirmed by determining ciclopirox olamine in commercial products. The results obtained were in good agreement with those found by potentiometric titration and the labelled values. The proposed GRM platform can be produced with high throughput and is cost-effective and disposable, hence no pre-treatment is required between measurements.

Determinação de ácido acéttico em amostra de vinagre adulterada com ácido clorídrico - um experimento integrado de titulação potenciométrica e condutométrica

The determination of acetic acid in vinegar adulterated sample using simultaneous potentiometric and condutometric titrations was used as an example of integrated experiment in instrumental analysis. An Excel® spreadsheet, which allows the entry of simultaneous data and the construction of the superimposed experimental curves (condutometric, potentiometric, first and second derivative potentiometric curve and, distribution diagrama of the acetic species as function of pH), was used as powerful tool to discuss the fundamental concepts involved in each technique and choose the best of them to quantify, without mutual interference, H3CCOOH and HCl in vinegar adulterated sample.