A new microelectrode method for simultaneous measurement of pH and PCO2

Area of Science:

• Biomedical Engineering
• Physiological Measurement
• Analytical Chemistry

Background:

• Accurate measurement of pH and partial pressure of carbon dioxide (PCO2) is critical for understanding physiological processes.
• Existing methods for simultaneous pH and PCO2 determination can be complex or invasive.
• Bicarbonate (HCO3) concentration is a key indicator of acid-base balance, often derived from pH and PCO2 measurements.

Purpose of the Study:

• To describe the fabrication and performance of a novel liquid-membrane microelectrode for simultaneous pH and PCO2 measurement.
• To evaluate the microelectrode's accuracy and reliability in physiological conditions.
• To assess the microelectrode's utility in measuring bicarbonate concentration in biological fluids and tissues.

Main Methods:

• Fabrication of a simple liquid-membrane pH-PCO2 microelectrode.
• Calibration and characterization of the microelectrode response in the physiological range at 37°C.
• In vivo measurements in rat renal proximal tubules and peritubular capillaries.
• Comparison of microelectrode-derived bicarbonate concentrations with directly measured values.

Main Results:

• The microelectrode demonstrated linear responses with near-Nernstian slopes for both pH and PCO2.
• PCO2 measurements were independent of solution pH, anionic composition, and serum proteins.
• In vivo measurements revealed distinct pH and PCO2 gradients within the rat kidney.
• Microelectrode-derived bicarbonate concentrations closely matched directly measured values in various biological samples.

Conclusions:

• The developed liquid-membrane microelectrode offers a simple and effective tool for simultaneous in vivo pH and PCO2 measurements.
• The microelectrode accurately determines bicarbonate concentrations, aiding in acid-base balance assessment.
• This technology has significant potential for physiological research and clinical diagnostics.