Evaluation of a same-metal PCB-based three-electrode system via impedance studies using potassium ferricyanide

We report for the first time the successful acquisition of electrochemical impedance spectroscopy data using an unconventional same-metal PCB-based three-electrode system. Conventional three-electrode systems primarily require expensive and bulky electrodes, and a high volume of analytes to conduct electrochemical impedance spectroscopy studies. The miniaturized PCB-based three-electrode system used in this work requires only trace amounts of analytes in the order of 10-20 μL owing to the design of the electrode sensor. Prominent standard redox probe potassium ferricyanide was used for impedance spectroscopic characterization studies. The results obtained were in congruence with existing literature; additionally the PCB-based three-electrode system demonstrated significantly higher repeatability, reproducibility, and consistency across different models of electrochemical instrumentations. Interestingly, the electrochemical impedance spectroscopy data of the PCB-3T sensor exhibited a consistent semi-circular impedance curve on a Nyquist plot and two distinct phase change regions on a Bode plot indicative of a simplified Randles cell model with an excellent circuit fit. Additionally this model provides an accurate impedance model for analysing trace analytes of potassium ferricyanide. Based on the circuit fitting model, potassium ferricyanide samples of varying concentrations at 1 mM, 5 mM, 10 mM, 15 mM and 20 mM demonstrated characteristic EIS charge transfer resistance corresponding to 435, 300, 233, 72 and 55 kΩ, respectively, and solution resistance of 260, 254, 218, 169 and 157 Ω, respectively. Therefore, the proposed novel same-metal three-electrode sensor can be employed in effective analysis and detection of samples with high accuracy and high sensitivity for trace amounts of analytes.