Determination of Cysteine in the Presence of Copper in Diluted Alkaline Electrolyte by Adsorptive Stripping Voltammetry at the Mercury Film Electrode

Abstract

A stripping method for the determination of cysteine in the presence of copper at the submicromolar concentration levels is described. The method is based on controlled adsorptive accumulation of cysteine at mercury film electrode followed by linear cyclic voltammetry scan measurement of the surface species. Optimum experimental conditions were found to be the use of a 1×10⁻³ M NaOH solution, an accumulation potential of −0.50 V and a scan rate of 200 mV. s⁻¹. The response of cysteine is linear over the concentration range 0.04–0.20 ppm. For an accumulation time of 15 minutes, the detection limit was found to be 0.9 ppb (7.4×10⁻⁹ M). The more convenient relation to measuring the cysteine in presence of metals, and others amino acids were also investigated. The utility of the method is demonstrated by presence of casein and ATP.

Keywords:

• Cysteine determination
• other amino acids
• copper
• other metals
• casein
• ATP
• thin‐film mercury electrode
• linear cyclic voltammetry(CV)

Acknowledgments

The authors gratefully acknowledge the CNPq and CAPES of the Government of Brazil and PUC‐Rio for support of this work. The experimental assistance of A. B. Neves is appreciated.