Thin-Layer Chemical Modulations by a Combined Selective Proton Pump and pH Probe for Direct Alkalinity Detection

Area of Science:

• Electrochemistry
• Analytical Chemistry
• Materials Science

Background:

• Traditional titration methods often require sampling and can be time-consuming.
• Precise control over ion concentrations is crucial for accurate chemical analysis.
• Thin-layer sample analysis presents challenges in achieving significant concentration gradients.

Purpose of the Study:

• To introduce a general concept for creating concentration perturbations in thin-layer samples using an electrochemical ion pump.
• To demonstrate the feasibility of in-situ titrations without sampling.
• To explore the potential for analyzing various ions in environmental and clinical settings.

Main Methods:

• Development of a selective electrochemical ion pump, specifically a proton pump using a polymeric membrane.
• Potentiometric assessment of hydrogen ion concentration using a second membrane.
• Application of constant potential modulation to induce proton concentration changes (up to 350 mM) in ~40 μL samples.
• Demonstration of acid-base titrations and total alkalinity determination in a river water sample.

Main Results:

• Successfully generated significant proton concentration perturbations (up to 350 mM) within seconds.
• Achieved comparable results for total alkalinity determination in river water (23.1 mM) versus standard methods (23.6 mM).
• Demonstrated the ability to perform in-situ acid-base titrations of NaOH and Na2CO3.

Conclusions:

• The electrochemical ion pump concept provides an effective method for in-situ generation of concentration perturbations in thin-layer samples.
• This approach eliminates the need for sampling and allows for rapid analysis.
• The technology is versatile and can be extended to the analysis of various ions, showing promise for environmental and clinical diagnostics.