No more conventional reference electrode: transition time for determining chloride ion concentration.

Area of Science:

• Electrochemistry
• Analytical Chemistry
• Materials Science

Background:

• Ion selective electrodes (ISE) are widely used for potentiometric ion determination.
• ISEs suffer from drift and require stable reference electrodes, limiting long-term in-situ applications.
• Measuring chloride ion concentration in electrolytes presents challenges for conventional methods.

Purpose of the Study:

• To develop a chronopotentiometric approach for chloride ion measurement that minimizes drift.
• To eliminate the requirement for a conventional reference electrode in ion concentration determination.
• To enable long-term, in-situ monitoring of chloride ions.

Main Methods:

• An anodic current pulse is applied to a Ag/AgCl working electrode.
• Chloride ion depletion near the electrode surface is monitored via potential change.
• The transition time (inflection point) is measured and correlated to chloride concentration using the Sand equation.

Main Results:

• The square root of the transition time shows a linear relationship with chloride ion concentration.
• Negligible drift (59 μM/day at 1 mM Cl-) was observed over two weeks.
• Transition time is tunable by adjusting the applied current pulse, demonstrating flexibility.

Conclusions:

• The chronopotentiometric method provides a drift-free and reference-electrode-independent approach for chloride ion measurement.
• This technique is suitable for long-term, integrated-sensor applications, including harsh environments like concrete structures.
• The method's independence from absolute reference potential allows for the use of simple pseudo-reference electrodes.