Improving the Sensitivity of Solid-Contact Ion-Selective Electrodes by Using Coulometric Signal Transduction

A1 Journal article (refereed)


Internal Authors/Editors


Publication Details

List of Authors: Han T, Mattinen U, Bobacka J
Publisher: American Chemical Society
Publication year: 2019
Journal: ACS Sensors
Journal acronym: ACS SENSORS
Volume number: 4
Issue number: 4
Start page: 900
End page: 906
Number of pages: 13
ISSN: 2379-3694
eISSN: 2379-3694


Abstract

A fundamental limitation of potentiometric ion sensors is their relatively low sensitivity due to the logarithmic dependence between potential and activity. Here we address this issue by exploring a recently developed coulometric transduction method for solid-contact ion-selective electrodes (SCISEs). Spin-coated thin-layer ion-selective membranes are used to lower the membrane resistance and shorten the response time of the SCISEs. When using coulometric transduction, an optimized design of the K+-SCISE is able to detect a concentration change of 5 mu M at a concentration level of 5 mM, corresponding to a 0.1% change in K+ activity. This indicates that SCISEs can provide extremely high sensitivity when employing coulometric transduction. Impedance measurements show that the coulometric transduction process for the K+-SCISE is limited by diffusion even for very thin ion-selective membranes. On the other hand, the H+-SCISE shows a low impedance and a fast coulometric response that is related to the high mobility of H+ in the H+-selective polymeric membrane as well as in the solid contact layer. The coulometric transduction method was used to detect small changes of pH in seawater and found to improve the sensitivity compared to classical potentiometry. The coulometric method was briefly tested also for determining activity changes of K+ in a serum sample.


Keywords

coulometric transduction, high sensitivity, IMPEDANCE, pH, seawater, Solid-contact ISE

Last updated on 2020-19-09 at 06:16