Percio Augusto Mardini Farias

Determination of Xanthine in the Presence of Hypoxanthine by Adsorptive Stripping Voltammetry at the Mercury Film Electrode

The complex Ni(II)-salen has been studied using cyclic and square-wave cathodic stripping voltammetry at the static mercury drop electrode in an aqueous media of phosphate and Hepes buffers (at pH 7.0). The resulting voltammograms consist of a totally irreversible one-electron transfer attributable to the coupling of Ni(II) salen/Ni(I) salen via an EC mechanism. The mean value for the transfer coefficientαin both supporting electrolytes was calculated as 0.35 ± 0.05. The amount of reactant adsorbed after 60 s of accumulation at −700 mV was calculated to be 2.8 × 10⁻⁸ mol·cm⁻². The detection limit for nickel determination was found to be 3.4 × 10⁻⁹ mol L⁻¹.

This paper describes a stripping method for the determination of acyclovir at the submicromolar concentration level. This method is based on controlled adsorptive accumulation of acyclovir at thin-film mercury electrode, followed by a linear cyclic scan voltammetry measurement of the surface species. Optimal experimental conditions include a NaOH solution of 2.0 × 10⁻³mol L⁻¹(supporting electrolyte), an accumulation potential of −0.40 V, and a scan rate of 100 mV s⁻¹. The response of acyclovir is linear over the concentration range 0.02 to 0.12 ppm. For an accumulation time of 4 minutes, the detection limit was found to be 0.42 ppb (1.0 × 10⁻⁹mol L⁻¹). More convenient methods to measure the acyclovir in presence of the didanosine, efavirenz, nevirapine, nelfinavir, lamivudine, and zidovudine were also investigated. The utility of this method is demonstrated by the presence of acyclovir together with Adenosine triphosphate (ATP) or DNA.

This paper describes a stripping method for the determination of lamivudine at the submicromolar concentration level. This method is based on controlled adsorptive accumulation of lamivudine at the thin-film mercury electrode followed by a linear cyclic scan voltammetry measurement of the surface species. The response of lamivudine is linear over the concentration range from 0.01 - 0.14 ppm. When there was an accumulation time of 4 minutes, the detection limit was found to be 0.13 ppb (5.7 x 10-10 mol L-1). More convenient methods to measure the lamivudine in the presence of the didanosine, acyclovir, nevirapine, nelfinavir, efavirenz and zidovudine were also investigated in this experiment. The utility of the method is demonstrated by the presence of lamivudine together with ATP or DNA.

A stripping method for the determination of didanosine at the submicromolar concentration levels is described. The method is based on controlled adsorptive accumulation of didanosine at thin-film mercury electrode followed by a linear cyclic scan voltammetry measurement of the surface species. Optimum experimental conditions include a NaOH solution of 2.0´10-3 mol L-1 (supporting electrolyte), an accumulation potential of -0.20 V, and a scan rate of 100 mV s-1. The response of didanosine is linear over the concentration range 0.01 – 0.10 ppm. For an accumulation time of 7 minutes, the detection limit was found to be 0.43 ppb (1.0´10-9 mol L-1). The more convenient relation to measuring the didanosine in presence of the metals ions, efavirenz, acyclovir, nevirapine, indinavir, nelfinavir, saquinavir, lamivudine and zidovudine were also investigated. The utility of the method is demonstrated by the presence of didanosine together with hypoxanthine, ATP or DN

This paper describes a stripping method for the determination of oseltamivir (Tamiflu) at the submicromolar concentration level. This method is based on controlled adsorptive accumulation of oseltamivir at the thin-film mercury electrode followed by a linear cyclic scan voltammetry measurement of the surface species. Optimum experimental conditions consist of a NaOH solution (pH 7-8) as supporting electrolyte, an accumulation potential of -0.40 V, and a scan rate of 100 mV s-1. The response of oseltamivir is linear over the concentration range from 0.0 – 0.5 ppm using lower accumulation time. When there was an accumulation time of 15 minutes, the detection limit was found to be 1.66 ppb (5.3 x 10-9 mol L-1). More convenient methods to measure the oseltamivir in the presence of the didanosine, acyclovir, nevirapine, nelfinavir, efavirenz, lamivudine and zidovudine were also investigated in this experiment. The utility of the method is demonstrated by the presence of oseltamivir together with hypoxanthine, ATP or DNA.

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 × 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 × 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.