The accuracy and limitations of a new meter used to measure aqueous carbon dioxide

TY - JOUR

T1 - The accuracy and limitations of a new meter used to measure aqueous carbon dioxide

AU - Moran, Damian

AU - Tirsgård, Bjørn

AU - Steffensen, John Fleng

PY - 2010/11/1

Y1 - 2010/11/1

N2 - The OxyGuard CO2 Analyzer is a novel meter that can directly measure aqueous CO2 gas pressure using a water-resistant gas-permeable membrane and infra-red absorption cell. The pCO2 is converted to a concentration via a solubility factor determined from the calibration procedure and a thermistor. We undertook to independently validate the precision and utility of this meter. Water flow over the probe membrane was a key determinant of the reaction time. At water velocities of ≥30cms-1 the time to 99% span was 6-7min, while at 0cms-1 it was 55-60min. Temperature and CO2(aq) concentration did not appreciably affect reaction time. The meter had a precision of ±0.5mgL-1 CO2(aq), and high linearity (correlation 0.99-1.01) above 1mgL-1 in both freshwater and seawater. The standard meter will not be useful for measuring low concentrations such as atmospheric CO2 levels, but will be useful in situations where accurate pH and carbonate alkalinity determinations are difficult to obtain, such as saline waters and waters of high organic loadings.

AB - The OxyGuard CO2 Analyzer is a novel meter that can directly measure aqueous CO2 gas pressure using a water-resistant gas-permeable membrane and infra-red absorption cell. The pCO2 is converted to a concentration via a solubility factor determined from the calibration procedure and a thermistor. We undertook to independently validate the precision and utility of this meter. Water flow over the probe membrane was a key determinant of the reaction time. At water velocities of ≥30cms-1 the time to 99% span was 6-7min, while at 0cms-1 it was 55-60min. Temperature and CO2(aq) concentration did not appreciably affect reaction time. The meter had a precision of ±0.5mgL-1 CO2(aq), and high linearity (correlation 0.99-1.01) above 1mgL-1 in both freshwater and seawater. The standard meter will not be useful for measuring low concentrations such as atmospheric CO2 levels, but will be useful in situations where accurate pH and carbonate alkalinity determinations are difficult to obtain, such as saline waters and waters of high organic loadings.

U2 - 10.1016/j.aquaeng.2010.07.003

DO - 10.1016/j.aquaeng.2010.07.003

M3 - Journal article

SN - 0144-8609

VL - 43

SP - 101

EP - 107

JO - Aquacultural Engineering

JF - Aquacultural Engineering

IS - 3

ER -