Symmetrical pH Electrochemical Cell Coupled to Constant Potential Coulometry for Improved Sensitivity and Precision:...

Area of Science:

• Oceanography
• Electrochemical Sensing
• Environmental Monitoring

Background:

• Seawater pH is crucial for ocean processes, but current spectrophotometry methods lack traceability and are prone to errors.
• Existing potentiometric pH glass electrodes have not seen significant performance improvements, hindering accurate in situ measurements.
• Manual sampling and analysis introduce errors like gas exchange, impacting data reliability.

Purpose of the Study:

• To enhance the sensitivity and precision of submersible pH probes using pH glass electrodes.
• To minimize systematic errors caused by temperature fluctuations and matrix effects.
• To implement a novel coulometric method for improved accuracy in ocean pH monitoring.

Main Methods:

• Developed a submersible pH probe incorporating pH glass electrodes in a symmetrical cell design.
• Minimized sensor drift and inaccuracies from liquid junction potentials and inner solution pH changes.
• Implemented a coulometric method and evaluated sensor calibration across various temperatures.
• Conducted in situ deployment and stability experiments in the Krka River Estuary.

Main Results:

• The developed submersible pH probe demonstrated a precision of 0.001 pH unit in situ.
• The probe approached ideal behavior during calibration over a range of temperatures.
• Recalibration procedures using synthetic seawater were evaluated for drift minimization.
• Depth profiles with varying salinity were successfully performed and compared with multiparameter probes.

Conclusions:

• The novel submersible pH probe offers significantly improved precision over existing routine probes.
• The integrated coulometric method and symmetrical cell design effectively reduce systematic errors.
• This advancement enables more accurate and reliable in situ monitoring of ocean pH and related processes.