Measuring xCO2 Using the CAT / NDIR Method:
System set-up, calibration, maintenance and shutdown

Maren E. Tracy, Edward T. Peltzer and Catherine Goyet
Marine Chemistry and Geochemistry Department
Woods Hole Oceanographic Institutiton
Woods Hole, MA 02543

Woods Hole Oceanographic Institution
Technical Report WHOI-94-01

February 1994.


Accurate measurement of the partial pressure of CO2 in seawater is currently performed by measuring pCO2 in an aliquot of a small volume of gas equilibrated with a large volume of seawater. pCO2 in the gas phase can be accurately measured either by gas chromatography or infra-red analysis. In order to minimize human labor to monitor pCO2 in surface seawater we opted for the infra-red analysis which does not require a highly trained person and which can easily be automated. This report describes how we have designed and automated a system for continual surface seawater pCO2 monitoring. It further indicates the necessary steps to set-up, run and maintain the system. With minor modifications, this system can also be used to measure pCO2 in discrete seawater samples.


Funding was provided by the Department of Energy under Grant FG02 94ER61544 to CMG.

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