Anodic stripping voltammetry and bismuth film electrode (BFE) were used to develop a method for the determination of lead in a complex sample (kerosene) prepared as a stable microemulsion. The method allowed the sensitive determination of lead with a quantification limit, in the sample, of 1.4 Â 10 À7 mol L À1 employing a 240 s accumulation time. Fortified sample analysis enabled the average analyte recovery around 99% which was statistically similar to the one achieved using a reference method (atomic absorption spectrometry). A detailed metrological evaluation was made including the calculation of the uncertainty associated to the voltammetric measurement indicating that repeatability (variations in the formation of different films and in the behavior of the analyte in the prepared microemulsions) is the main contribution of measurement uncertainty.
Pesticide air pollution by spraying was evaluated under different temperature, humidity and wind climatic conditions in Brazil. Field experiments were performed with application towards the soil and in guava orchards, where spray dispersion was monitored by adding p-aminobenzoic acid (PABA), a fluorescent substance, as a tracer to the water contained in the spray tanks. Samples were collected with filter membranes (Whatman 180025), and the PABA was extracted from the filters by shaking with water in a Petri dish and measured in a spectrofluorometer. A spray aimed towards the soil with filters positioned on the ground and hung at different heights did not show different upward dispersion as observed when lateral pulverization was conducted. In this case, a tractor with a sprayer moved through a 3 m high and 6 m wide frame with filter membranes mounted at 60 cm intervals. Spray dispersion patterns were modified by guava leaf resistance. No influence of temperature and humidity was observed in this short-lived spraying process. Nevertheless, wind drift can occur during airborne dispersion and is an important pesticide pollution source which requires control. Droplets with PABA powered by assisted spraying upwards returned to the ground by gravity and, therefore, did not constitute a vertical source of atmospheric pollution.
Recebido em 6/10/11; aceito em 30/11/11; publicado na web em 23/1/12 A simple and sensitive method has been proposed for the determination of sibutramine-HCl in energy drinks, green tea and pharmaceutical formulations using differential pulse voltammetry performed on a hanging mercury drop electrode. In the chosen experimental condition (Mcllvaine pH 4.0 buffer, 50 mV pulse amplitude and 40 mV s -1 scan velocity), sibutramine-HCl presented a reversible behavior and a peak maximum at -80 mV. Detection limit was 0.4 mg L -1 and the working linear range extended up to 33.3 mg L -1 (r = 0.99). Analysis of real and fortified samples enabled recoveries between 91 and 102%. The electroanalytical method was compared with a HPLC method which indicated it accuracy.
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