Electrochemical stripping analysis from micro-counter electrode
Résumé
Electrochemical stripping analysis (anodic, cathodic, or adsorptive) is usually based on the preconcentration of a target analyte on the working electrode surface and then measuring its quantity via its direct quantitative electrochemical transformation (with the electrode refreshed afterwards). In this work, we demonstrate a new approach to carry out electrochemical stripping analysis, not based on the analyte being directly pre-concentrated on the working electrode (WE), but on the signal obtained indirectly from the counter electrode (CE). Different from the CE with large surface area in classical electrochemical measurements, microelectrode is chosen here as CE to purposely use the polarization effect. The concept is based on oxidizing the analyte on WE in one compartment of the electrochemical cell while reducing Cu 2+ on CE from another compartment connected with a metal or ionic "bridge". The deposited Cu on CE is then analyzed by stripping in another cell, and the charge shows good linear relationship with the concentration of analyte. As the stripping current (peak) is much clearer than the different in the direct oxidation current, it improves the resolution of raw signal. Besides, it may also reduce the background signal from blank solution by "filtering" the non-Faradaic charge. Like in classical electrochemical stripping analysis, one may also prolong the oxidation time in exchange for higher sensitivity of analysis. This work extends the applications of stripping analysis and offers a new angle of electroanalysis by capturing signals from counter electrode.
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