The CO2 conductivity electrode, a fast-responding CO2 microelectrode

Area of Science:

• Biomedical Engineering
• Analytical Chemistry
• Sensor Technology

Background:

• Accurate and rapid measurement of carbon dioxide (CO2) is crucial in various scientific and medical applications.
• Existing CO2 sensing technologies may face limitations in response time or sensitivity.
• Development of microscale sensing systems is essential for in-situ and minimally invasive measurements.

Purpose of the Study:

• To present a novel, fast-responding CO2 microelectrode system.
• To investigate the relationship between system design, carrier water flow rate, and performance metrics (sensitivity, response time).
• To analyze the hydrodynamical and kinetic factors influencing CO2 measurement accuracy.

Main Methods:

• A double-lumen catheter with a CO2-permeable membrane and a stainless steel tip was employed.
• The system utilized a carrier fluid (bidistilled water) flushed at a constant flow rate.
• Changes in water conductivity, measured by a conductivity cell, correlated with the partial pressure of CO2 (PCO2) in the surrounding medium.

Main Results:

• The system demonstrated a fast response time, with 90% deflection achieved in approximately 4 seconds when sensors were placed within 10 mm of the membrane.
• Response time increased to about 10 seconds at a distance of 45 cm from the membrane (at 5 ml/min flow rate).
• A trade-off between sensitivity and response speed was observed, influenced by carrier water flow rate.

Conclusions:

• The developed CO2 microelectrode system provides a sensitive and rapid method for PCO2 determination.
• Optimizing carrier water flow rate and sensor proximity to the membrane are key for achieving desired response characteristics.
• The findings contribute to the advancement of microfluidic sensing technologies for CO2 monitoring.