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Analyser for total alkalinity in seawater


HydroFIA TA analyzer

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The CONTROS HydroFIA® TA is a flow through system for the determination of the total alkalinity in seawater. It can be used for continuous monitoring during surface water applications as well as for discrete sample measurements. The autonomous TA analyser can be easily integrated into existing automated measuring systems on voluntary observing ships (VOS) such as FerryBoxes.

Total alkalinity is an important sum parameter for many scientific fields of application including ocean acidification and carbonate chemistry research, monitoring of biogeochemical processes, aqua culture / fish farming as well as pore water analysis.

Operating principle

A defined amount of seawater is acidified by injection of a fixed amount of hydrochloric acid (HCl).

After acidification the generated CO2 in the sample is removed by means of a membrane based degassing unit resulting in a so-called open-cell titration.

The subsequent pH determination is carried out by means of an indicator dye (Bromocresol green) and VIS absorption spectrometry.

Together with salinity and temperature, the resulting pH is directly used for the calculation of total alkalinity.


  • Measurement cycles of less than 10 min
  • Robust pH determination using absorption spectrometry
  • Single-point titration
  • Low sample consumption (<50 mL)
  • Low reagent consumption (100 μL)
  • User-friendly “Plug and Play” reagent cartridges
  • Minimized biofouling effects due to acidification of the sample
  • Autonomous long-term installations


  • Integration into automated measuring systems on VOS
  • Cross-flow filters for high turbidity / sediment loaded waters
  • External pump

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