Total organic carbon definition

Water for injection (WFI) is the most widely used solvent for parenteral preparations. The USP requirements for WFI and purified water have been recently updated to replace the traditional wet and colorimetric analytical methods with the more modern and cost-effective methods of conductivity and total organic carbon. Water for injection must be prepared and stored in a manner to ensure purity and freedom from pyrogens. The most common means of obtaining WFI is by the distillation of deionized water. This is the only method of preparation permitted by the European Pharmacopoeia (EP). In contrast, the USP and the Japanese Pharmacopeias also permit reverse osmosis to be used. The USP has also recently broadened its definition of source water to include not only the U.S. Environmental Protection Agency National Primary Drinking Water Standards, but also comparable regulations of the European Union or Japan. 

Dissolved organic carbon (DOC) is by definition the organic carbon content of a sample which was prefiltered through a 0.45 pm filter, whereas total organic carbon (TOQ is the carbon content of an... 

The nomenclature of organic carbon is described in detail in Chapter 2 and in the Glossary. While there is a difference in definition between total organic carbon (TOQ and dissolved organic carbon (DOC), which is that the DOC is that part of TOC which passes through a 0.45 om filter, in this thesis the terms are used interchangeably. 

Total carbon includes dissolved organic material (called total organic carbon, TOC) and dissolved COf and HCOJ (called inorganic carbon, IC). By definition, TC = TOC + IC. To distinguish TOC from IC, the pH of a fresh sample is lowered below 2 to convert COl and HCO J into CO2, which is purged from (bubbled out of) the solution with N2. After IC has been removed, combustion analysis of the remaining material measures TOC. IC is the difference between the two experiments. 

The FTT synthesis has given less impressive results, having produced only 11 definite and 8 tentative matches (Yoshino et al., 1971 Hayatsu et al., 1971). Total yields were 0.01-0.1%, much less than in the Miller-Urey synthesis (2%), though similar to the abundance in meteorites ( 0.1% of the organic carbon). The product. distribution again was fairly similar to that in meteorites, but also included aromatic or heterocyclic amino acids such as tyrosine and histidine that cannot be made by conventional Miller-Urey syntheses. In the present context, that is a liability rather than an asret, since these amino acids have not been found in meteorites either. 

In the early days following the discovery of chirality it was thought that only molecules of the type CWXYZ, multiply substituted methanes, were important in this respect and it was said that a molecule with an asymmetric carbon atom forms enantiomers. Nowadays, this definition is totally inadequate, for two reasons. The first is that the existence of enantiomers is not confined to molecules with a central carbon atom (it is not even confined to organic molecules), and the second is that, knowing what we do about the various possible elements of symmetry, the phrase asymmetric carbon atom has no real meaning. 

Case 3. The raindrop now runs off the calcite rock and flows into a calcium-carbonate-ffee soil, where carbon dioxide is added from the decomposition of organic matter until the total CO2 is five times its original value. For simplicity, it will be assumed that no other components are added and no other reactions take place between the soil and the raindrop. In this case calcium concentration and total alkalinity are constant, and the total CO2 and initial concentrations are known. From the definition of terms and equilibrium relations we can write ... 

Artificial life is an entirely new approach to the fundamental problems of biology, because it allows us to study life in a totally different way, i.e. by building machines that have some of its properties. It must be underlined, however, that silicon-based life is utterly different from carbon-based life because artificial molecules and artificial cells are made of electronic circuits and are therefore two-dimensional creatures. This explains why biologists have not abandoned more traditional approaches, and the search for a proper definition of organic life has never stopped. In this field, an important step forward was made in 1974 by Francisco Varela, Humberto Maturana and Ricardo Uribe, with the paper that introduced in biology the concept of autopoiesis. 

Equilibrium capacity for adsorption of organic solutes on carbon can be predicted to increase with decreasing temperature since adsorption reactions are exothermic. The differential heat of adsorption, AH, is defined as the total amount of heat evolved in the adsorption of a definite quantity of solute on an adsorbent. Heats of vapor phase adsorption... 

Environmental criteria have been established for many of these, but the utility and applicability of such criteria for indoor environments is controversial for at least four reasons. Eor example, the goals of the threshold limit values often do not include preventing irritation, a primary concern in indoor environments with requirements for close eye work at video display terminals. For most of the pollutant categories, the problem of interactions, commonly termed the multiple contaminants problem , remains inadequately defined. Even for agents that are thought to affect the same receptor, such as aldehydes, alcohols, and ketones, no prediction models are well established. Finally, the definition of representative compounds for measurement is unclear. That is, pollutants must be measurable, but complex mixtures vary in their composition. It is unclear whether the chronic residual odor annoyance from environmental tobacco smoke correlates better with nicotine, particulates, carbon monoxide, or other pollutants. The measure total volatile organic compounds is meanwhile... 

Many other organic acids important in water chemistry have p/Cg values similar to that of acetic acid, for example, propionic acid and butyric acid. Many natural waters contain silicates and organic bases that contribute to the total alkalinity. Wastewaters contain substantial quantities of organic bases, ammonia, and phosphates. Anaerobic digester supernatant often contains high concentrations of bases similar to acetate, as well as carbonates, ammonia, and phosphates. For very complex systems for which a detailed chemical analysis is not available, no attempt is made to work with the mathematical definition of alkalinity. However, if the system is chemically defined we can show that these substances will contribute to alkalinity if, during the titration, some of the base is converted to the conjugate acid. We can modify the total alkalinity definition to include these species so that... 

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