Double-barreled K+-selective microelectrodes based on dibenzo-18-crown-6

Area of Science:

• Electrochemistry
• Biomedical Engineering
• Analytical Chemistry

Background:

• Liquid ion-exchanger microelectrodes (e.g., Corning code 477317) exhibit high sensitivity to quaternary ammonium ions, potentially impairing potassium (K+) activity measurements.
• Accurate measurement of intracellular K+ is crucial for understanding various physiological processes.

Purpose of the Study:

• To develop and characterize a novel neutral carrier microelectrode for selective K+ detection.
• To compare the performance of the new microelectrode against existing Corning microelectrodes, particularly in the presence of interfering ions.

Main Methods:

• A neutral carrier microelectrode was constructed using dibenzo-18-crown-6 as the ionophore.
• Both crown ether and Corning microelectrodes were calibrated in solutions containing various cations, including K+, Na+, and quaternary ammonium ions.
• Intracellular K+ activity was measured in Necturus gallbladders using both types of microelectrodes.

Main Results:

• Crown ether microelectrodes demonstrated significantly higher selectivity for K+ over quaternary ammonium ions and imidazole compared to Corning microelectrodes.
• Selectivity factors (log K(ij)K) for the crown ether microelectrodes showed greatly improved K+ discrimination.
• No significant differences were observed in intracellular K+ activity measurements between the two microelectrode types.

Conclusions:

• The neutral carrier microelectrode based on dibenzo-18-crown-6 offers enhanced selectivity for K+ measurement.
• This improved selectivity overcomes the limitations of conventional ion-exchanger microelectrodes in complex biological samples.
• The developed microelectrode is a valuable tool for accurate intracellular K+ determination.