Carbon analysis – methods and applications

Carbon analysis (also called CO2 analysis or carbonate analysis) is used to determine the total carbon content or the content of different carbon fractions in a variety of sample materials.

It is carried out on coal, coke, petrol, secondary fuels, lime stone, stones, ores, ashes, plants and soils to measure concentrations of total carbon (TC), total organic carbon (TOC) or total inorganic carbon (TIC).

Carbon analysis with combustion analyzers is a standardized method consisting of the following steps: weighing the sample, adding accelerators if required, combustion of the sample in an oxygen stream and measurement of the combustion gases, usually with infrared cells.

Carbon analysis is a routine process used in production control, incoming/outgoing goods inspection, industrial R&D and scientific research at universities. There are various other methods to measure carbon concentrations.


Carbon analysis methods

Other methods to determine the carbon content, besides carbon analysis with combustion analyzers, are coulometry, gravimetry, ICP, spark spectroscopy. Each method has its particular strengths and weaknesses, but all of them, including combustion analysis, have a detection limit for carbon of approximately 0.5 to 1 ppm. Lower detection limits of carbon can only be achieved with mass spectroscopy and adequately trained staff.

When applied correctly, combustion analysis provides the carbon content over a wide measurement range (from 1 ppm to 100%) easily, quickly and safely without requiring specially trained personnel. Combustion analysis complies with a variety of national and international standards such as DIN, ISO, ASTM.

Fractional carbon and water analysis

Beside the analysis of the total carbon content, it is also possible to determine single fractions of carbon. By changing the combustion temperature in a multiphase analyzer during the measurement process, it is possible to detect different carbon and water fractions. The latter result from the moisture of the sample and from the oxidization of organic C-H compounds. The various carbon (TOC, TIC, TC) and water (moisture, chemically combined water) fractions are detected at different combustion temperatures.

Another way of determining the carbon fractions – which is also described in the relevant standards – is the use of acid. The sample is mixed with acid and then either the carbon dioxide from the carbonate is measured (TIC) or the remaining organically bound carbon (TOC). Combustion analyzers are also suitable for this differential measurement.