Ionophore-Based Voltammetric Ion Activity Sensing with Thin Layer Membranes.

Area of Science:

• Electroanalytical Chemistry
• Chemical Sensing
• Membrane Science

Background:

• Thin-layer ion-selective membranes offer simultaneous multi-ion detection.
• Poly-3-octylthiophene (POT) backside contact facilitates ion release via potential scans.

Purpose of the Study:

• To provide fundamental evidence for ion discrimination using thin multi-ionophore membranes.
• To establish a cyclic voltammetry method for simultaneous and selective ion analysis.
• To calculate ion-selective constants and apply the method to real-world samples.

Main Methods:

• Fabrication of thin-layer (200 ± 25 nm) multi-ionophore membranes with POT backside contact.
• Cyclic voltammetry to interrogate ion activity and observe characteristic potential peaks.
• Varying cation-exchanger concentration to identify rate-limiting factors.
• Thermodynamic modeling of ion transfer processes.

Main Results:

• Observed multiple voltammetric peaks, each corresponding to a specific ion (Li+, K+, Na+).
• Demonstrated that cation-exchanger concentration, not POT film, limits ion transfer charge.
• Calculated apparent stability constants for Li+, K+, and Na+ that align with potentiometric methods.
• Successfully determined Li+, Na+, and K+ in artificial samples and Li+, K+ in human plasma within a single scan.

Conclusions:

• Thin-layer multi-ionophore membranes coupled with cyclic voltammetry enable simultaneous and selective ion detection.
• The system can be modeled thermodynamically under optimized conditions.
• This technique is a viable analytical tool for complex biological samples.