Ultratrace Xanthine Determination in Diluted Alkaline Electrolyte by Adsorptive Stripping Voltammetry at the Mercury Film Electrode

Abstract

A stripping method for the determination of xanthine at the submicromolar concentration level is described. The method is based on controlled adsorptive accumulation of xanthine at a thin-film mercury electrode followed by a linear scan voltammetry measurement of the surface species. Optimum experimental conditions were found to be the use of a 5.0 × 10⁻³ M NaOH solution, an accumulation potential of 0.00 V, and a scan rate of 20 mV s⁻¹. The response of xanthine is linear over the concentration range 20–140 ppb. For an accumulation time of 30 min, the detection limit was found to be 36 ppt (2.3 × 10⁻¹⁰ M). The more convenient relations for measuring xanthine in the presence of the metals, hypoxanthine, amino acids, and other nitrogenated bases were also investigated. The utility of the method is demonstrated by the presence of xanthine in adenosine-5′-triphosphate or DNA.

Keywords:

• Amino acids
• ATP
• DNA
• hypoxanthine
• linear scan stripping voltammetry
• metals
• nitrogenated bases
• thin-film mercury electrode
• xanthine determination

The authors gratefully acknowledge the CNPq and CAPES of the government of Brazil and PUC-Rio for their support of this work. The experimental assistance of Anselmo Bezerra Neves is appreciated.