Total organic carbon

Total organic carbon (TOC) is the amount of carbon found in an organic compound and is often used as a non-specific indicator of water quality or cleanliness of pharmaceutical manufacturing equipment. TOC may also refer to the amount of organic carbon in soil, or in a geological formation, particularly the source rock for a petroleum play; 2% is a rough minimum. For marine surface sediments, average TOC content is 0.5% in the deep ocean, and 2% along the eastern margins. Total organic carbon (TOC) is the amount of carbon found in an organic compound and is often used as a non-specific indicator of water quality or cleanliness of pharmaceutical manufacturing equipment. TOC may also refer to the amount of organic carbon in soil, or in a geological formation, particularly the source rock for a petroleum play; 2% is a rough minimum. For marine surface sediments, average TOC content is 0.5% in the deep ocean, and 2% along the eastern margins. A typical analysis for total carbon (TC) measures both the total carbon present and the so-called 'inorganic carbon' (IC), the latter representing the content of dissolved carbon dioxide and carbonic acid salts. 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 an acidified sample with carbon-free air or nitrogen prior to measurement, and so is more accurately called non-purgeable organic carbon (NPOC). Since the early 1970s, TOC has been an analytic technique used to measure water quality during the drinking water purification process. TOC in source waters comes from decaying natural organic matter (NOM) as well as synthetic sources. Humic acid, fulvic acid, amines, and urea are examples of NOM. Some detergents, pesticides, fertilizers, herbicides, industrial chemicals, and chlorinated organics are examples of synthetic sources. Before source water is treated for disinfection, TOC provides an estimate of the amount of NOM in the water source. In water treatment facilities, source water is subject to reaction with chloride containing disinfectants. When the raw water is chlorinated, active chlorine compounds (Cl2, HOCl, ClO−) react with NOM to produce chlorinated disinfection byproducts (DBPs). Researchers have determined that higher levels of NOM in source water during the disinfection process will increase the amount of carcinogens in the processed drinking water. With passage of the U.S. Safe Drinking Water Act in 2001, TOC analysis emerged as a quick and accurate alternative to the classical but more lengthy biological oxygen demand (BOD) and chemical oxygen demand (COD) tests traditionally reserved for assessing the pollution potential of wastewaters. Today, environmental agencies regulate the trace limits of DBPs in drinking water. Recently published analytical methods, such as United States Environmental Protection Agency (EPA) method 415.3, support the Agency's Disinfectants and Disinfection Byproducts Rules, which regulate the amount of NOM to prevent the formation of DBPs in finished waters. The content of TOC is also an important parameter to evaluate the quality of organic shale resources which are one of the most important unconventional fuels. Numerous evaluation methods have been introduced, including these based on wireline logs and in situ techniques. Introduction of organic matter into water systems occurs not only from living organisms and from decaying matter in source water, but also from purification and distribution system materials. A relationship may exist between endotoxins, microbial growth, and the development of biofilms on pipeline walls and biofilm growth within pharmaceutical distribution systems. A correlation is believed to exist between TOC concentrations and the levels of endotoxins and microbes. Sustaining low TOC levels helps to control levels of endotoxins and microbes and thereby the development of biofilm growth. The United States Pharmacopoeia (USP), European Pharmacopoeia (EP) and Japanese Pharmacopoeia (JP) recognize TOC as a required test for purified water and water for injection (WFI). For this reason, TOC has found acceptance as a process control attribute in the biotechnology industry to monitor the performance of unit operations comprising purification and distribution systems. As many of these biotechnology operations include the preparation of medicines, the U.S. Food and Drug Administration (FDA) enacts numerous regulations to protect the health of the public and ensure the product quality is maintained. To make sure there is no cross-contamination between product runs of different drugs, various cleaning procedures are performed. TOC concentration levels are used to track the success of these cleaning validation procedures especially