Electrochemical Detection of Mercaptans in Wine Using Gold Nanoparticle-Modified Carbon Electrodes

Abstract

The organoleptic virtues of wine can be damaged by the presence of compounds produced during fermentation or aging, such as mercaptans. This work presents an environmentally friendly electrochemical sensor for the easy detection of mercaptans in wine samples, using glassy carbon and screen-printed carbon electrodes. The modification of the carbon working electrodes with gold nanoparticles increased the sensitivity and selectivity of the procedures, considering the strong covalent bond that forms readily between sulfur and gold atoms. Ethanethiol reduction has been shown to depend both on pH and on adsorption time since the electrode is immersed in the solution until the voltammogram is recorded. The highest current has been recorded in a supporting electrolyte solution at pH 4.2 with an adsorption time of 10 min in the case of gold nanoparticle modified glassy carbon electrodes and pH 3 and 90 s for gold nanoparticle screen-printed carbon electrodes. The developed procedures reach a reproducibility of 7.9% (n = 7), based on the slopes associated with different calibration curves registered in the concentration range from 7.7 to 36.6 μg l−1 when using gold nanoparticle modified glassy carbon electrodes and 7.2% (n = 5) in the case of gold nanoparticle modified screen-printed carbon electrodes (concentration range, from 1.6 to 10.9 μg l−1). The sensors have successfully been applied to the detection of ethanethiol, representing mercaptans, in white and red wines.