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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.

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This paper describes a stripping method for the determination of zidovudine at the submicromolar concentration levels. This method is based on the controlled adsorptive accumulation of zidovudine at the thin-film mercury electrode, followed by a linear-sweep stripping voltammetry measurement of the surface species. Optimal experimental conditions include a NaOH solution of 2.0 × 10 -3 mol·L -1 (supporting electrolyte), an accumulation potential of -0.30 V and a scan rate of 100 mV·s -1 . The response of zidovudine is linear over the concentration range 0.01 -0.08 ppm. After an accumulation time of 5 minutes, the detection limit was found to be 0.67 ppb (2.5 × 10 -9 mol·L -1 ). More convenient methods to measure zidovudine concentration in the presence of the didanosine, acyclovir, nevirapine, lamivudine, and efavirenz, were also investigated. The presence of zidovudine together with ATP or ssDNA demonstrates the utility of this method.

Highly sensitive, simple and inexpensive techniques of adenine determination are particularly interesting in relation to the present development of ATP and DNA sensors. A nanomolar concentration of adenine can be determined in the presence of copper. For an accumulation time of 30 minutes, the detection limit found was 0.22 ppb (1.63 Â 10 À9 M). The method is based on controlled adsorptive accumulation of adenine-copper at thin-film mercury electrode followed by linear scan voltammetric measurement of the surface species. By applying a condition time of 60 s at À 0.9 V, the same thin-film can be used over several measurements. Optimum experimental conditions were found to be the use of a 5.0 Â 10 À3 M NaOH solution, an accumulation potential over the À 0.20 to À 0.40 V range, and a scan rate of 100 mV s À1 . The response of adenine-copper is linear over the concentration range 20 -100 ppb. The more convenient ways to measuring adenine in the presence of metals and other nitrogenated bases were also investigated. The adenosine triphosphate (ATP) or deoxyribonucleic acid (DNA) are first treated with acid (e.g., 0.1 M perchloric acid), and the acid-released adenine (without separation from others products of the degradation) is directly determined by adsorptive stripping voltammetry.

This paper describes a stripping method for the determination of nevirapine at the submicromolar concentration levels. The method is based on controlled adsorptive accumulation of nevirapine at thin-film mercury electrode, followed by a linear cyclic scan voltammetry measurement of the surface species. Optimal experimental conditions include a 2.0 x 10(-3) mol L(-1) NaOH solution (supporting electrolyte), an accumulation potential of -0.20 V, and a scan rate of 100 mV s(-1). The response of nevirapine is linear over the concentration range 0.01-0.14 ppm. For an accumulation time of 6 minutes, the detection limit was found to be 0.87 ppb (3.0 x 10(-9) mol L(-1)). More convenient methods to measure the nevirapine in presence of the efavirenz, acyclovir, didanosine, indinavir, nelfinavir, saquinavir, lamivudine, zidovudine and metals ions were also investigated. The utility of this method is demonstrated by the presence of nevirapine together with ATP or DNA.

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