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322

TOTAL ORGANIC CARBON-COMBUSTION METHOD

Summary

This analytical method quantitatively determines the total organic carbon in all forms of soil.  This method combines acid fumigation with a dynamic flash combustion system that is coupled with a gas chromatographic (GC) separation system and thermal conductivity detection (TCD) system.  Acid fumigation with HCl vapor removes inorganic carbon with no loss of organic carbon.  The analytical method is based on the complete and instantaneous oxidation of the sample by “flash combustion” which converts all organic and inorganic forms of carbon into CO2.  The method has a detection limit of approximately 0.02% carbon.

This method may not be appropriate for highly calcareous soils.  Studies on soils containing 50% carbonate show that acid fumigation treatment may not be completely effective in removing carbonates.

Sample material must be ground to the consistency of fine powder for this analysis.

Sample amount requested:  2 g

Questions concerning limited sample size can be answered by the UC Davis Analytical Laboratory

Harris, D., Horwáth, W. R.  and Van Kessel, C.  2001.  Acid fumigation of soils to remove carbonates prior to total organic carbon or CARBON-13 isotopic analysis.  Soil Science Society of America Journal 65:1853-1856 (2001.) 

AOAC Official Method 972.43, Microchemical Determination of Carbon, Hydrogen, and Nitrogen, Automated Method, in Official Methods of Analysis of AOAC International, 16th Edition (1997), Chapter 12, pp. 5-6, AOAC International, Arlington, VA.