Total Organic Carbon (TOC): TOC is the sum measure of the concentration of all organic carbon covalently bonded in the organic molecules of a given sample. TOC may also refer to the amount of organic carbon in a geological formation.

Applications of TOC: TOC is often used as a non-specific indicator of water quality while having numerous other applications including, (i) the first chemical analysis on potential petroleum source rock in oil exploration, (ii) detecting contaminants in drinking water (iii) environmental monitoring, and (iv) industrial water and process management.

Instrument: In our lab, TOC is analyzed using Shimadzu TOC-V_CHS analyzer which is capable of measuring  total carbon (TC), inorganic carbon (IC), and non-purgeable Organic Carbon (NPOC) within a detection range of 5 - 25,000 ppb. Combining SSM-5000A with the TOC-V_CHS permits analysis of many solid samples in addition to aqueous samples, including soil, sludge, and sediments. Combining the ASI-V automatic sampler ASI-V with the TOC-V creates a fully automatic analysis system, enhancing features and convenience with easier operation.

Principle of Analysis: TC is measured by injecting a portion  of the sample into a heated combustion unit packed with an oxidation catalyst. In Shimadzu TOC-V_CHS, combustion of samples is achieved by heating them to 680 ^oC in an oxygen-rich environment inside the TC combustion unit filled with a platinum catalyst, either a platinum coated ceramic bead or platinum infused quartz wool for high efficiency analysis. This process converts carbon in sample into carbon dioxide (CO₂). This carbon dioxide is carried with the carrier gas stream from the combustion unit to a NDIR (non-dispersive infrared gas analyzer) and the concentration of carbon dioxide is measured. The TC concentration of the sample is obtained by using the calibration curve prepared with standard solutions.

At the same time, a similar injection of sample enters IC reaction chamber filled with phosphoric acid solution. All IC is converted to carbon dioxide and concentration of carbon dioxide is measured with the NDIR.

TOC concentration is quickly obtained as the difference of TC and IC.