Dissolved Inorganic Carbon Analyzers

NEW Dissolved Inorganic Carbon Analyzer

Characterize inorganic carbon in an aquatic carbonate system

LI-5300A Dissolved Inorganic Carbon Analyzer

Why Measure Dissolved Inorganic Carbon (DIC)?

DIC measurements help researchers better understand the role of aquatic systems in the global carbon cycle—especially in the context of ocean acidification and climate change. DIC measurements provide insights into carbon behavior—such as carbon sources, sinks, and fluxes.

DIC and the corresponding isotopic δ¹³C signature measurements benefit research disciplines including:

Ocean acidification
Climate change
Geochemical-based carbon cycle research
Carbon behavior in a water column
Porewater from sediment cores

Calculation of carbonate parameters
Algae applications (e.g., algae biofuels)
Net productivity measurements
Carbon dioxide removal and sequestration
Oil and gas industry applications

What is DIC?

When carbon dioxide (CO₂) gas dissolves in water, it forms carbonic acid (H₂CO₃), which then dissociates into various constituents—including protons (H⁺), bicarbonate ions (HCO₃^-), and carbonate ions (CO₃^2-). Dissolved inorganic carbon (DIC) is the combined total of these carbon containing species expressed as a CO₂ equivalent concentration. The concentrations of each constituent can be influenced by the system's pH, partial pressure of CO₂ (pCO₂), and total alkalinity. Figure 1 shows how the balance between carbonic acid, carbonate, and bicarbonate is affected by pH.

Figure 1. The Bjerrum plot, or the carbonate speciation diagram, depicts the equilibrium concentrations of inorganic carbon species in an aquatic solution as a function of pH.

Advantages of the DIC System

Takes precise measurements across a wide range of values
Can extract 100% of CO₂ from water samples in 2 minutes
Stationary on ships and laboratories
Suited for culturing and incubation measurements

How is it Measured?

LI-5300A

Each DIC analyzer includes a required secondary gas analyzer. The LI-7815 CO₂/H₂O Trace Gas Analyzer is ideal for precise seawater measurements.

The DIC analyzer and gas analyzer work in tandem to accurately measure DIC in a water sample. The DIC analyzer is composed of a Tecan XLP6000 syringe pump, a 12-port valve system, a Peltier condenser, a mass flow controller, and a computer with proprietary software for data collection and analysis.

LI-5350A

Each DIC analyzer includes a required secondary gas analyzer. The LI-850 CO₂/H₂O Analyzer is ideal for precise freshwater measurements, but sacrifices precision to achieve a more compact form factor

All DIC configurations consist of core module which contains a reactor, syringe pump, sample selection valve, and sample conditioning. An external computer is included with proprietary software for data collection and analysis. The LI-5350A is the only one with an internally mounted gas analyzer.

LI-5370A

The DIC analyzer acidifies a water sample in a reactor which forces all inorganic carbon species into gas phase CO₂. That CO₂ is swept from the reactor by a carrier gas and is carried to a CO₂ analyzer. The CO₂ measurements are totalized to compute total DIC, along with the δ¹³C ratio in the LI-5370A. Total DIC measurements are reported in μmol/L or μM. Measurements of calibration standards for DIC (and δ¹³C for LI-5370) are interspersed with sample measurements to ensure overall measurement accuracy.

The LI-5370A is supplied with an external gas analyzer, as well as the core module which contains a reactor, syringe pump, sample selection valve, and sample conditioning. An external computer is also included with proprietary software for data collection and analysis.

For more details about each combination of DIC and gas analyzer, see the chart below:

DIC Systems from LI-COR

DIC Analyzer	Measured Parameters	Precision (1σ)
LI-5300A DIC Analyzer with LI-7815	Total DIC	0.1% @ 2000 umol/L
LI-5350A DIC Analyzer with LI-850	Total DIC	0.15%@ 2000 umol/L
LI-5370A Isotopic Dissolved Inorganic Carbon DIC Analyzer with LI-7825	Total DIC and δ¹³C DIC	0.15% @ 2000 umol/L

* Measuring multiple aliquots from the same sample container is recommended.

The DIC analyzer uses a method that acidifies a water sample to release CO₂ gas and allow for the detection and quantification of the evolved CO₂. The acidification process forces all inorganic carbon species into the gas phase as CO₂—which allows the gas analyzer to then quantify CO₂.

These gas measurements, in conjunction with sample data, are then used to compute the water sample's DIC concentration. All DIC measurements are reported in μmol/L.

Specifications

General

Power supply: 100 to 240 VAC 50/60 Hz
Power requirements:

DIC Module: 120W max
External Computer: 95W max
Gas Analyzer: LI-7815/LI-7825 65W max; LI-850 14W max
Computer operating system: Windows^® 10 (included)

Number of Sample Ports: 8
Operating environment: Indoor
Operating temperature: 15 to 28°C recommended. Temperature fluctuations may affect measurement precision.
Operating humidity: Up to 85%, non-condensing
Dimensions: 43 x 27 x 47 cm (H x W x D) not including externally mounted gas analyzer or computer

LI-5300A

Gas analyzer: LI-7815; included; externally mounted
Carrier gas: Compressed air with constant CO₂concentration; regulated between 16 and 18 PSI
Precision (1σ): ± 0.1% at 2000 μmol/L
Accuracy: Determined by uncertainty of calibration standards and precision
Measurement time: ~ 4 minutes per measurement
Sample volume^1,2: 0.5 to 4 mL per measurement

LI-5350A

Gas analyzer: LI-850; included; internally mounted
Carrier gas: CO₂-free compressed air or N₂; regulated between 16 and 18 PSI
Precision (1σ): 0.15% at 2000 μmol/L
Accuracy: Determined by uncertainty of calibration standards and precision
Measurement time: ~ 4 minutes per measurement
Sample volume ^1,2: 0.2 to 1.5 mL per measurement

LI-5370A

Gas analyzer: LI-7825; included; externally mounted
Carrier gas: Compressed air with constant CO₂concentration; regulated between 16 and 18 PSI
Precision (1σ): 0.1% at 2000 μmol/L
Precision δ¹³C (1σ): ± 0.04%
Accuracy: Determined by uncertainty of calibration standards and precision
Measurement time: ~ 4 minutes per measurement
Sample volume^1,2: 0.5 to 4 mL per measurement

Specifications subject to change without notice.

References

Dickson, A., C. Goyet (1994). DOE Handbook of Methods for the Analysis of the Various Parameters of the Carbon Dioxide System in Sea Water, Version 2.

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