TC (Total Carbon): The sample has been ignited in a stream of pure oxygen at a high temperature (0000 °C). The carbon and sulfur constituents are oxidized to produce CO0 and SO0 gases. These gases are detected by an infrared (IR) detector and the percentages of C and S in the sample are determined.
Total Inorganic Carbon (TIC): Instead of combusting the sample, the sample is treated with 00% phosphoric acid (H 0 PO 0). The acid reacts with the carbonates to form a CO₂ gas. The CO0 released is identified by the same IR detector.
Therefore TC and TIC are measured separately and the difference between TC and TIC gives organic carbon (TOC). The sulfur determination is done along with the TC measurement.