Response Patterns of Chromoionophore-Based Bulk Optodes Containing Lipophilic Electrolytes: Toward...

Area of Science:

• Analytical Chemistry
• Materials Science

Background:

• Ion-selective optical sensors (optodes) offer advantages but are limited by dual-ion response.
• Practical applications require sensors independent of background electrolyte composition.

Purpose of the Study:

• To develop a theoretical and experimental method for achieving single-ion activity sensing with optodes.
• To demonstrate the independence of H+ cation activity measurements from background electrolyte concentrations.

Main Methods:

• Numerical simulation of optode response.
• Experimental validation using chromoionophore-based optodes doped with lipophilic electrolytes (including ionic liquids).
• Thin-film spectrophotometry and digital color analysis.

Main Results:

• Theoretical proof of concept for single-ion optical response using lipophilic electrolytes.
• Established correlation between interfacial potential stability and single-ion optical response.
• Experimental data quantitatively support theoretical predictions, showing independence from background cation concentration.

Conclusions:

• Introduction of lipophilic electrolytes into optode membranes enables selective H+ cation activity assessment.
• The developed approach overcomes the limitation of dual-ion dependence in traditional optodes.
• This method offers a significant advancement for accurate ion sensing in complex solutions.