The determination of dissolved carbon is an essential analytical prerequisite in many agronomic and environmental problems in aqueous media: detection of organic contaminants in soils, control of the decomposition of organic matter from the soil surface, etc.
In these various contexts, the use of a carbon analyzer is particularly judicious when organic substances appear at low concentration levels.
Following a purely operational logic, the TOC L analyzer separates the different forms of carbon by their "purgeability", that is to say the tendency of these substances to leave the solution when they are displaced by a current of gas (sparging technique).
Then each fraction is oxidized in an oven at 680°C and the CO2, product of combustion, is measured by non-dispersive infrared spectroscopy (NDIR). The CO2 is measured by the NDIR detector in the form of a peak. The concentrations are obtained by comparison with a calibration carried out under strict same conditions from potassium hydrogen phthalate. This technique can detect concentrations between 0.1 and 1000 ppm.
The nomenclature of dissolved carbon:
TC : Total Carbon (TIC + TOC)
TIC: Total Inorganic Carbon (CO2, H2CO3, HCO3-, ect)
TOC: Total Organic Carbon (NPOC + POC ou TC - TIC)
NPOC: Non Purgeable Organic Carbon (all organic compounds in natural waters excluding volatiles)
POC: Purgeable Organic Carbon (volatile organic compounds: pesticides, synthetic pollutants, ect)
Applications of this method:
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in the clay fraction (f <2 µm) of soils and in sediments
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in solutions extracted from acid forest soils and in the liquid phase of hydromorphic soils downstream of agricultural plots
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in rainwater, rivers, lysimeters in forest ecosystems
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in soil and river waters in areas of permafrost thawed in the context of global warming
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measurement of different forms of carbon in river water, waste water, sea water