An evaluation of ultrathin ring and band microelectrodes as amperometric sensors in electrochemical flow cells

Abstract

AbstractGold and platinum ultrathin ring microelectrodes (0.1–0.5 mm thick, 1.5–4 mm diameter) were made by sputtering, from fired metalloorganic paint, and from foil for use as sensors in a thick‐layer wall‐jet flow cell. An end‐on array of three 0.1 μm × 0.5 mm gold band electrodes were mounted parallel to the flow direction in a thin‐layer channel cell. These ultrathin sensors, along with a jet‐centered carbon microdisk, were evaluated in the amperometric flow‐injection mode for temporal stability, calibration sensitivity, detectivity, background signal, and flow rate dependence of the analytical signal using ferrocene samples in acetonitrile containing 10−4–10−2 M TEAP. The detectivity of gold paint ring electrodes made on borosilicate glass was 3–6 nM, an order of magnitude lower than any of the other electrodes tested. Analytical signals from gold paint and foil rings and the carbon microdisk had the best temporal stability. The current for the ultrathin band array in a channel cell was flow rate‐independent, and the exponential dependence of cell current on flow rate was 0.11–0.14 for ultrathin rings in the thick‐layer wall‐jet mode.