Electronic control of constant potential capacitive readout of ion-selective electrodes for high precision sensing

[摘要] Constant potential capacitive readout of ion-selective membranes offers better sensitivity than traditional potentiometry by giving an easily identifiable transient current spike, which can be integrated to give a charge proportional to logarithmic of ion activity. Some concerns of this technique include complex fluidic handling, longer measurement times, baseline drifts and memory effects arising from excess charge accumulation on the capacitor. This work describes an electronic circuit strategy to automate the switching procedure, resulting in rapid and reproducible measurements. In contrast to earlier work, alternating to a reference solution is no longer required for establishing a new current baseline. The open-circuit potential is measured before performing chronoamperometry and its value is applied directly to the sample solution. The intermittent discharging of the capacitor by electronic circuit assures that the potential difference across the capacitor returns again to zero. This electronic capacitive readout system was applied to measure sodium concentration using a 10 mu F capacitor to amplify the signal. The precision was found to be improved over direct potentiometry, corresponding to 0.11 mmol L- 1 NaCl and 0.13 mmol L- 1 NaCl for standard solutions and pooled serum sample, respectively. Using the automated electronic system for ion measurement makes the system more robust while resulting in fast and reliable quantitative measurements.

[发布日期] 2021-10-01

[关键词] Capacitive readout;Sodiu m;Seru m;Electronic switch;Capacitor