Organics protocol, physical/chemical

WHAT IS THE PHYSICAL/CHEMICAL BASIS OF THE ERA S ORGANICS PROTOCOL ... 

Which determinative technique to use is dictated by the physical and chemical nature of the analyte of interest. The organics protocol flowchart introduced in Chapter 2 serves as a useful guide. Let us consider how we would determine which instrumental technique to use for the following example. Ethylene glycol, 1,2-ethanediol (EG), and 1,2-dichloroethane (1,2-DCA) consist of molecules that contain a two-carbon backbone with either a hydroxyl- or chlorine-terminal functional group. The molecular structures for these are as follows ... 

Another characteristic to take into account is that ATP is an endogenous component of the cells, both somatic and bacterial. Therefore, an extraction step must to be included in the assay protocol it is very simple and quick to perform. Several extraction methods have been reported, both physical and chemical, such as heating and the use of surfactants, trichloroacetic acid, and organic solvents [89, 120, 121], The chemical methods are generally preferred the addition of a surfactant can be effective in most cases. The use of mild or strong extraction... 

Pollutant realism Is achieved when the test system Includes sufficient diversity of components and the physical and chemical properties so that the pollutant behaves In the test system as it would In nature. Pollutant realism Is lacking because, In most test protocols, the pollutant does not Interact with any part of the environment, except the organism. A lack of pollutant realism In traditional tests may result In overestimates of risk. As an example, substantial Information Is now available about the toxicity of TCDD to numerous species when they are exposed via Injection, Incubation, diet, or dermal application. At Times Beach, Missouri, the TCDD is In the soli, and because It has apparently been there for some time, It is probably tightly bound to the soil. Little Is published about the toxicity of TCDD bound to soil, for any means of exposure. Intuitively, I suspect the TCDD Is less toxic when bound to soil than In the forms commonly used In toxicity testing. Thus, the risks of TCDD-lnduced toxicity to humans at Times Beach may be much smaller than would be suggested by the results of traditional testing which lacks this aspect of pollutant realism. 

Jehkin, M.E., S.M. Saunders, V. Wagner, and M.J. Pilling Protocol for the development of the Master Chemical Mechanism, MCM v3 (Part B) tropospheric degradation of aromatic volatile organic compounds. Atmospheric Chemistry and Physics, 3 (2003) 181-193. 

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