ABSTRACT
The electrochemical behavior of Saccharomyces cerevisiae sp was studied using a glassy carbon electrode (GCE) modified with Nafion-dispersed oxidized multi-walled carbon nanotubes (OMWCNT). The morphology was studied using scanning electron microscopy (SEM), showing that the yeast sticks to the carbon nanotube surface instead of the glassy carbon surface. The redox couple Fe(CN)6 4-/Fe(CN)6 3- was used to determine the electroactive area and the heterogeneous transfer constant, which increased 80.5% and 108% respectively by the presence of nanotubes. The studies of the pH effect showed that the anodic potential decreases at alkaline pH and that the highest current intensity occurs at a pH value of 7.00. Studies of the scan rate effect have shown that yeast oxidation is an irreversible mixed control process in which two electrons participate. The relationship between yeast concentration and the anodic current density was studied using different electrochemical techniques obtaining the best analytical parameters through chronoamperometry. The linear range was between 3.36 and 6.52 g L-1, the limit of detection (LOD) and the limit of quantification (LOQ) were 0.98 g L-1 and 3.36 g L-1 respectively, and the sensibility obtained was 0.086 µA L g-1 mm-2. These results show that the multi-walled carbon nanotubes in water and Nafion® allow obtaining an anodic signal corresponding to the yeast, which facilitates its quantification through electrochemical methodologies, favoring the reduction of analysis times and costs compared with other techniques.
