Total Organic Carbon
Organic matter in soils and sediments is widely distributed over the earth’s surface occurring in almost all terrestrial and aquatic environments. Soils and sediments contain a large variety of organic materials ranging from simple sugars and carbohydrates to the more complex proteins, fats, waxes, and organic acids.
Total Organic Carbon (TOC) is quite simply the organic carbon within a sample. However, it will not include the organic carbon from volatile compounds as these are lost during digestion and drying. TOC is a parameter in the Waste Acceptance Criteria (WAC) test. TOC is the only true measure of organic carbon present in a soil.
TOC methods utilise heat and oxygen, chemical oxidants or a combination of these to convert organic carbon to Carbon dioxide (CO2). The evolved CO2 is then measured.
The determination of total organic carbon is an essential part of any site characterisation or ecological assessment since its presence or absence can markedly influence how chemicals will react in the soil or sediment.
Total Organic Compounds Testing Methodology
- To test for Total Organic Carbon, a weighed portion of the air dried and ground sample is treated with sulphurous acid at 40°C for 16 hours in order to remove any inorganic carbon species which react to form carbon dioxide. The excess sulphurous acid is then evaporated off.
- The sample is combusted at 1600°C in an oxygen atmosphere using an induction furnace
- The combustion gases then pass through an infra-red cell which measures the carbon dioxide (CO2) concentration.
- The total quantity of carbon, which is now purely organic carbon, is calculated and reported as a percentage of the original mass of sample.
The main advantage of using this technique is that the elevated temperatures ensure the combustion of all the carbon forms present. At SOCOTEC, we have an automated high throughput method for the Analysis of TOCs and can offer fast turnaround times.
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