Equipment

UIC Coulometer and the Miranda VINDTA3D acidification unit
for automated Total Inorganic Carbon (TIC) analysis

Coulometer image The UIC Coulometer provides the capability of analyzing TIC in solids and liquids. Coulometery is an extremely reliable and precise method for measuring inorganic carbon, a methodology that has been in use for decades. UIC has been fabricating coulometers for scientific and commercial use for decades, and has earned a solid reputation for excellence.

At the S-LAB, we combine two self-contained units for sample acidification to evolve CO2, which is then introduced into the UIC coulometer for precise and accurate coulometric detection. One sample introduction unit is designed for solids, and the other for liquids, and each are described below:

  1. The UIC front-end acidification unit (CM5230) is designed for solid samples, and includes the following features: option to select different acids; option to heat the sample; option to add wetting/emulsifying agents; and option to modify flow path and scrubbers to optimize for a particular application.
  2. The Marianda VINDTA 3D is designed for the extraction of CO2 from seawater. The VINDTA 3D offers automated sample handling and titration, salinity determination, and enhanced precision in sample delivery permitting high precision (± 1 µmol/kg) coulometric detection required for dissolved inorganic carbon analysis of seawater.

After acidification using one of the front-end units, the evolved CO2 is measured on the UIC CM5015 Coulometer. Employing the principles of Faraday’s Law, the coulometer automatically measures the absolute mass of carbon dioxide evolved from sample acidification. No user-calibration is required, and linear detection is achievable from less than 1 ug carbon to over 10,000 ug carbon. Because the coulometric process is 100% efficient, precisions of 0.2% relative standard deviation or better are common for standard materials. Additionally, it is possible to analyze either solid or liquid samples. The UIC Coulometer is the instrument of choice for dissolved inorganic carbon analyses as outlined in the standard operating protocol prepared by the DOE Carbon Dioxide Survey Science Team (1994).

S-LAB Accuracy and Precision Analysis (PDF)

References

DOE (1994) Handbook of methods for the analysis of the various parameters of the carbon dioxide system in sea water. Version 2, A. G. Dickson & C. Goyet, eds. ORNL/CDIAC-74