Simultaneous monitoring of pH, CO2 and O2 using an optical imaging fiber

The interdependence of pH, CO2 and O2 during chemical and biochemical processes has driven the need to monitor them simultaneously, continuously and in situ, in order to exert better control over such reactions. We present the fabrication and performance of a multi-analyte imaging fiber sensor that allows pH, CO2 and O2 to be monitored simultaneously with rapid response. Sensing elements are fabricated by covalently immobilizing fluorescent indicators within polymer matrices via photopolymerization, resulting in the formation of distinct regions of analyte-sensitive polymer at the fiberʹs distal end. The multianalyte sensorʹs working range is 0%–100% for O2 and 0%–10% for CO2 in the pH range 5.5–7.5. The sensor was used to monitor the pH, CO2 and O2 changes during a beer fermentation.