Total organic carbon - high frequency induction furnace, volumetric (6B2)

This method for total soil OC involves production, purification and measurement of CO₂ evolved when soil carbon is ignited in a stream of O₂. Because all C compounds are converted to CO₂, the C from carbonates, charcoal, undecomposed wood, etc, will be included, as no soil pre-treatment is specified. In the volumetric sub-method 6B2a, concentrated KOH solution is used to absorb the CO₂ released. The difference between the original volume of gas in the burette and the volume produced after ignition equals the volume of CO₂ evolved from the sample, after correction for gas temperature and pressure. Sub-method 6B2b is similar to Method 6B2a, except the CO₂ produced by ignition is measured via infrared / thermal conductivity detection. Both 6B2a and 6B2b use finely-milled air-dry sample, with weights varying with expected C concentrations. Surrogate estimates can be obtained by NIR (method 6B4a) or MIR (method 6B4b) reflectance spectroscopy. The methods specify reporting as %C on an oven-dry (105^oC) basis.