Total organic carbon
From Freepedia
TOC, Total organic carbon — The amount of carbon bound in organic compounds. Often used as an indicator of water quality or cleanliness of pharmaceutical manufacturing equipment.
A typical analyis for TOC measures both the total carbon (TC) present as well as the inorganic carbon (IC, or carbonate). Subtracting the inorganic carbon from the total carbon yields TOC. Another common variant of TOC analysis involves removing the IC portion first and then measuring the leftover carbon. This method involves purging the acidified sample with carbon-free air prior to measurement, and so is more accurately called non-purgeable organic carbon (NPOC).
Virtually all TOC analyzers measure the CO2 formed when organic carbon is oxidized and/or when inorganic carbon is acidified. Oxidation is performed either through Pt-catalyzed combustion or with a UV/persulfate reactor. Once the CO2 is formed, it is measured by a detector: either a conductivity cell (if the CO2 is aqueous) or a non-dispersive infrared cell (if the CO2 is gaseous). Modern TOC instruments are cabable of detecting carbon concentrations as low as 50 µg/L.
