An electrochemical stripping procedure is described for trace measurements of adenine by adsorption on a static mercury drop electrode. Cyclic voltammetry was used to characterize the interfacial and redox behavior. Optimum experimental conditions were found when using a 0.001 M NaOH solution, initial potential of þ 0.01 V, scan rate of 5 mV s À1 and linear scan mode. The response of free adenine is linear over the 2125 ORDER REPRINTS concentration range 0.25-1.25 ppm. Linear scan voltammetry, without accumulation yields a detection limit of 55 ppb adenine. Proper conditions were tested to measuring adenine in presence of guanine, acridine orange, copper, zinc and ssDNA.

An electrochemical stripping procedure for trace measurements of thymine is described by adsorption on a static mercury drop electrode. Cyclic voltammetry was used to characterize the interfacial and redox behavior. Optimum experimental conditions were found to be the use of a 0.005 M NaOH solution, an initial potential of À 0.08 V, a scan rate of 100 mV.s À 1 and a linear scan mode. The response of free thymine is linear over the concentration range 0.1-0.5 ppm. Linear scan voltammetry, without acumulation time yields a detection limit of 62 ppb thymine. Acridine orange and copper were also investigated for measuring thymine in the presence of guanine. 1295

A stripping method for the determination of single-stranded DNA in presence of copper at the submicromolar concentration levels is described. The method is based on controlled adsorptive accumulation of adenine (from acidtreated DNA) at thin-film mercury electrode followed by linear scan voltammetry measurement of the surface species. Optimum experimental conditions were found to be the use of a 5.0 Â 10 À3 M NaOH solution, an accumulation potential of À 0.40 V and a scan rate of 200 mV s À1. The response of adenine -copper is linear over the concentration range 50 -250 ppb. For an accumulation time of 15 minutes, the detection limit was found to be 4 ppb. The more convenient relation to measuring the ssDNA in presence of metals and nitrogenated bases were also investigated. The utility of the method is demonstrated by the presence of adenosine-triphosphate (ATP) and amino acids.

No abstract

Um método de redissolução para a determinação do agente anti-retroviral efavirenz em concentrações submicromolares e meio eletrolítico alcalino diluído é descrito. As condições experimentais ótimas encontradas são: NaOH 2,0 × 10 -3 mol L -1, potencial de acumulação −0,10 V, amplitude de pulso 50 mV e velocidade de varredura 50 mV s ). As condições mais convenientes para a medida da concentração de efavirenz na presença de ATP, DNA, diversos metais e outros antivirais foi também investigada. A utilidade do método é demonstrada pela determinação de efavirenz em uma mistura sintética contendo lamivudina e zidovudina, drogas frequentemente usadas na clínica em associação com o efavirenz como parte da terapêutica anti-retroviral de alta ação (HAART).A stripping method for the determination of the antiretroviral drug efavirenz at the submicromolar concentration levels in diluted alkaline electrolyte is described. Optimum experimental conditions were: 2.0 × 10 -3 mol L -1 NaOH, accumulation potential of −0.10 V, pulse amplitude of 50 mV and scan rate of 50 mV s ). The most convenient conditions to measure the efavirenz concentration in the presence of ATP, DNA, several metals, and other antiviral drugs was also investigated. The utility of the method is demonstrated by the determination of efavirenz in a synthetic mixture containing both lamivudine and zidovudine, which are frequently used in the clinic in association with efavirenz as part of highly active antiretroviral therapy (HAART).

A stripping method for the determination of adenosine triphosphate (ATP) in presence of copper at the submicromolar concentration levels is described. The method is based on controlled adsorptive accumulation of ATP-copper at thin-film mercury electrode followed by linear DC or cyclic voltammetry scan measurement of the surface species. Optimum experimental conditions were found to be the use of a 1 Â 10 23 M NaOH solution, an accumulation potential of 20.40 V and a scan rate of 200 mV . s 21 . The response of ATP-copper is linear over the concentration range 0.2-1.2 ppm. For an accumulation time of 30 min, the detection limit was found to be 14 ppb (2.5 Â 10 28 M). The more convenient relation to measuring the ATP in presence of metals, adenine and amino acids were also investigated.

No abstract

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 × 10−3 mol 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 × 10−9 mol 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.