Evaluation of platinum electrodes and three electrode potential standards to determine electrode quality
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The pre-installation evaluation of Pt electrodes in electrode potential (EH) standards is crucial for reliable field interpretations. During a routine check of electrode quality in three different EH standards before field installation, inconsistent and variable results were recorded. Due to the preliminary observational results, the objectives of this study were to: (i) elucidate why EH readings in the same buffer were different before and after soaking in water, (ii) identify the most rigorous standard for detecting poor electrode function, and (iii) determine causation for disparity in the electrode performance in EH standards when using constructed EH electrodes. Electrodes were evaluated in quinhydrone in pH 4 and pH 7 buffers and ferrous-ferric sulfate solutions. Additionally, an experiment was developed to intentionally expose Cu in EH electrodes with decreasing area of the metal exposed. Finally, aqueous macroscopic electrochemical and Fourier Transform Infrared spectroscopic evaluations of Cu in the three standards were conducted to characterize and quantify the reduction-oxidation reactions of Cu. This study found that quinhydrone in pH 7 buffer was not a rigorous standard for determining improper function of Pt electrodes constructed utilizing Cu wire. Due to the interrelationship between the reduction-oxidation potential of Cu and pH, standards with low pH proved to be a more rigorous standard. Soil Science Society of America.