Dissolved CO2 Systems

Dissolved CO2 (DCO2) Systems are designed to measure dissolved pCO2 in water at atmospheric pressure.  The systems are composed of a DCO2 sampler with accessories, a non-dispersive infra red CO2 analyzer with a built in gas pump, data interface and software. The Rapid Response DCO2 System consists of flow through Rapid DCO2 Sampling System, liquid pump, IRGA with built in gas pump, data interface and software.

The DCO2 sampler is the key component of the standard system as it samples pCO2 from the liquid and carries it to the IRGA.  The DCO2 sampler is  covered with  PTFE (polytetrafluoroethylene) membrane which allows it to be submerged in water (up to 2 ft).  The CO2 gas dissolved in water diffuses across the PTFE membrane into the sampler and is carried to the CO2 analyzer in a closed loop fixed volume gas stream for detection.  Liquid flow past the sampler is necessary and stirring is required for the system to work well.  A Rapid Response DCO2 System with a flow-through design is also available.  It employs the DCO2 sampling system where water is circulated through silicone tubules and gas passess on the other side of the tubules in the opposite direction.  CO2 gas then diffuses across the tubules from water to the gas stream and is carried to the CO2 sensor for measurements. Contact Qubit Systems for details.

DCO2 Sampler – standard system
Rapid DCO2 Sampling System

The PTFE membrane is permeable to gases but not to water at atmospheric pressure.  The system detects dissolved partial pressure of CO2 in water and is insensitive to carbonates.  Note that this determination of CO2 partial pressure is not based on pH measurements.   The DCO2 Systems can be configured for various ranges of CO2 concentrations from ppm to 100% in gas phase.

Note that the response time of the standard system is slow (4-10 min) due to diffusion across the PTFE membrane.  The response time depends on the flow of the liquid past the DCO2 sampler, hence good stirring of the solution is essential.  The response time of the flow-through Rapid DCO2 System is faster 2 to 4 min.

  • Measure dissolved CO2 in fresh and seawater
  • Customized to desired pCO2 range (ppm to 100%)
  • Based on diffusion of CO2 out of the liquid
  • Based on infrared gas analysis
  • Insensitive to carbonates
  • NOT based on pH measurements


Sample data from standard DCO2 System :

Sample respirometry data from small gold fish using Rapid Response DCO2 System