Optical pH, oxygen and carbon dioxide monitoring using a microdialysis approach

Microdialysis coupled with optical absorbance or fluorescence measurement has been used to monitor pH, pCO2, and pO2 in blood and buffer solutions. The system employs micro-flow streams of reagents, a simple optical system and a method of achieving steady microliter per minute flow rates. When integrated in a recirculating flow loop, the sensor has an excellent resolution in the physiologic range in buffer of ±0.003 pH units, ±0.5 mm Hg pCO2, and ±1.5 mm Hg pO2 with response times in heparinized bovine blood of 4.8 min, 1.8 min, and 2.1 min for pH, pCO2, and pO2, respectively.