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:
in the clay fraction (f <2 µm) of soils and in sediments
in solutions extracted from acid forest soils and in the liquid phase of hydromorphic soils downstream of agricultural plots
in rainwater, rivers, lysimeters in forest ecosystems
in soil and river waters in areas of permafrost thawed in the context of global warming
measurem ent of different forms of carbon in river water, waste water, sea water