Electrochemical impedance spectroscopy in nitrate solutions containing monosodium glutamate using screen-printed electrodes

Electrochemical impedance spectroscopy technique has been used to characterize commercial screen-printed electrodes (SPEs) in monosodium glutamate (MSG) aqueous solutions at open-circuit potential and room temperature. Additionally, considerations have been made about the chemical nature of existing species (undissociated MSG molecules, glutamate ions and zwitterions) and have processed the conductivity data from literature by calculating and selecting specific conductivity for diluted MSG solutions, 0.5 M KNO3 and 0.5 M NaNO3. In first experiments, SPEs based on Au, Pt and carbon (graphite) materials were studied in 1 mM MSG dissolved in deionized water Nyquist and Bode spectra were comparatively recorded only on gold SPEs in 100 μM and 1 mM MSG solutions having 0.5 M nitrate salts (KNO3 or NaNO3) as supporting electrolyte. In addition to the capacitive behavior, inductive loops attributed to competitive adsorption between glutamate species and nitrate ions were highlighted. Fitting of experimental data with three equivalent circuits as models has allowed the evaluation of impedance parameters related to charge transfer rate, double layer capacity and adsorption components (resistance, inductance, and capacitance). © 2020, Politechnica University of Bucharest. All rights reserved.