Evaluation of the electrochemical response of Saccharomyces cerevisiae using screen-printed carbon electrodes (SPCE) modified with oxidized multi-walled carbon nanotubes dispersed in water – Nafion®

The evaluation of the electrochemical determination of Saccharomyces cerevisiae was carried out using a screen-printed carbon electrode (SPCE) modified with Nafion-dispersed oxidized multi-walled carbon nanotubes (OMWCNT). The morphology was studied using scanning electron microscopy (SEM), showing a complete modification of the surface with the nanotubes and yeast interaction with them instead of the graphite surface. The redox couple Fe(CN)(6)(4−)/Fe(CN)(6)(3−) was used to determine the electroactive area, the heterogeneous transfer constant, and the Nafion® effect. Results showed increases in electroactive area and heterogeneous transfer constant of 146% and 20.4%, respectively, due to the presence of nanotubes. Studies of the Nafion® effect showed that the polymeric membrane affects the electroactive area but not the heterogeneous transfer constant. Studies of the scan rate effect show that yeast oxidation is an irreversible mixed control process. As the concentration and scan rate increased, the anodic potential shifted toward more anodic values. The relationship between yeast concentration and the anodic current density (current/electroactive area) of yeast showed a linear range between 0.61 and 7.69 g L(−1), the limit of detection (LOD) and the limit of quantification (LOQ) were 0.17 g L(−1), and 0.61 g L(−1), respectively, and the sensibility obtained was 0.03 μA L g(−1) mm(−2). These results show that with the screen-printed carbon electrodes it is possible to improve the electrochemical determination of this microorganism, enhancing the analytical parameters and quantification, allowing greater portability and decreasing measurement times and associated waste.