DIC-δ13C Analyzer

Model AS-D1

The Apollo SciTech® DIC-δ13C analyzer is designed for simultaneous and precise analyses of dissolved inorganic carbon (DIC) and δ13C for natural water samples and is based on the Picarro G-2131i CO2/H2O Analyzer. The analyzer consists of a digital syringe pump for precise delivery of reagent and sample solutions (KLOEHN, USA), a mass flow controller to accurately regulate the carrier gas flow rate, a specifically designed CO2  stripping reactor that allows for an efficient and smooth stripping of CO2 from the water sample, an electronic cooling system for removing moisture, and a computer communication assembly.

The analyzer has a broad analytical range as the sample and standard volume can be changed by users (currently tested for 1 – 7 ml). This feature is useful for the analysis of seawater and coastal waters. As coastal samples often have large concentration differences and thus require a variable volume and a 100% extraction of CO2  from the sample within a reasonable period. The analyzer has a relatively fast processing rate and high precision. The current model is designed for automatic sampling from multiple sample bottles in a lab or continuous underway analysis on board a ship.

Below: demo unit of the Apollo Scitech DIC-δ13C Analyzer (model AS-D1) together with a Picarro G-2131i Analyzer.

Additional Information

A typical integration curve/peak with time is given below. The peak is almost symmetrical. DIC is the area integration under the curve. δ13C is the average of signal when CO2 concentration is above 350 ppmv.

pCO2 vs. integration time and δ13C vs. time.


  • Precision (DIC): ± 0.1% for seawater
                                      (or ± 2 µmol/kg)
  • Precision (DIC-δ13C): ± 0.07%
  • Sample volume: 1 – 7 ml per analysis
  • Time: < 12 min per analysis
  • Software: Apollo SciTech software included
  • Power Supply: Universal (100 – 240V, 50/60 Hz)
  • Carrier Gas: Compressed air (with a CO2 scrubber)
  • Environment: Land and shipboard laboratories
Note: a Picarro’s G-2131i Carbon Isotope Analyzer should be provided by the user.

Other Picarro models that measure the isotopic ratio of CO2 may be compatible. Consult for details.