Metal complexing agent

Metal Complexing Agent Supporting Electrolyte Detection Limit, (m) Reference... 

Synergy between primary and secondary anti-oxidants occurs and often a mixture is employed. Also included are metal complexing agents, e.g., EDTA (ethylenediaminetetraacetic acid), citric acid, the purpose of which is to deactivate extraneous metal ions that catalyse polymer oxidation. 

Chlorine is the major anion in surface- and mantle-derived fluids. It is the most abundant anion in hydrothermal solutions and is the dominant metal complexing agent in ore forming environments (Banks et al. 2000). Despite its variable occurrence, chlorine isotope variations in natural waters conunonly are small and close to the chlorine isotope composition of the ocean. This is also true for chlorine from fluid inclusions in hydrothermal minerals which indicate no significant differences between different types of ore deposits such as Mississippi-Valley and Porphyry Copper type deposits (Eastoe et al. 1989 Eastoe and Guilbert 1992). 

The bipyridines are dibasic, and the two acid dissociation constants Ki and K2, for all the bipyridines have been determined. Typical values are recorded in Table I. There has been considerable interest in the first dissociation constants Ki of 2,2 -bipyridine and substituted 2,2 -bipyridines because of their use as metal complexing agents. In general, the order of relative basic strengths of derivatives of 2,2 -bipyridine is as expected. Electron-attracting substituents reduce the basicity, whereas electron-donating substituents increase the basicity of the molecule. " The dissociation constants of several substituted bipyridines correlate well with the Hammet equation. 2,2 -Bipyridines with an electron-donating substituent at position 4 are monoprotonated at N-1 and not at... 

As mentioned earlier, it has proven difficult to precipitate uniform metal (hydrous) oxides by direct mixing of solutions of metal salts and bases, especially of concentrated ones. Instead, it is possible to control the generation of hydroxide ions in situ, which can be achieved if certain organic compounds, such as formamide or urea, are slowly decomposed in aqueous solutions of metal salts. The rate of these processes depends on the pH, temperature, concentration of the reactants, and the presence or absence of metal complexing agents. In particular, precipitations caused by reactions in solutions of urea have been widely employed, although the products consist primarily of metal carbonates or basic metal carbonates. For this reason, this method is described in more detail in Chapter 7.1 of this volume. 

The importance of 1,10-phenanthroline and substituted 1,10-phenanthrolines as metal complexing agents and their use in analytical applications has provided the impetus for an extensive study of procedures for their synthesis.182 The original synthesis of 1,10-phenanthroline by a double Skraup reaction on o-phenylenediamine using glycerol and sulfuric acid in the presence of an oxidizing agent continues to attract attention, and various improvements in reaction... 

Applications of imidazole-modified polymers have been primarily concerned with utilization as catalysts and metal complexing agents. 

In zinc metalloenzymes. zinc is a selective stoichiometric constituent and is essential for catalytic activity. It is frequently present in numerical correspondence with the number of active enzymatic sites, coenzyme binding sites, or enzyme subunits Removal of zinc results in loss of activity. Inhibition by metal complexing agents is a characteristic feature of zinc metalloenzymes. However, no direct relationship holds between the inhibitory effectiveness of these agents and their affinity for ionic zinc. Although zinc is the only constituent of zinc metalloenzymes in vivo, it can be replaced by other metals m vitro, such as cobalt, nickel, iron, manganese, cadmium, mercury, and lead, as m the case of carboxy-peprida.ses. 

Metal Complexing agent Detection limit, nM Reference... 

Bush AI. 2002. Metal complexing agents as therapies for Alzheimer s disease. Neurobiol Aging 23 1031-1038. 

Matrices Trace Metals Complexing Agents Determination Methods... 

The cyanide ion is extremely important as a metal complexing agent,... 

Heat treatment is effective in deactivating the enzymes. Metal complexing agents may deactivate the enzyme by making the copper unavailable. 

Figure 9.52 Structure of the SP-encoded primary peptidomimetic library of metal complexing agents L37 and of the monomer sets M1-M4 used for its synthesis.

In the early 1970s, Zitko et al. (1973) noted that HAs reduced the activity of the free Cu " ion, as measured by the copper ion-selective electrode, and that this effect was quite well correlated with the observed toxicity of Cu(II) to salmon. Soon thereafter, Pagenkopf et al. (1974) also reported on the effect of complexation on the toxicity of copper to fishes. Sunda and Guillard (1976) demonstrated that the activity of the free Cu " ion in synthetic growth media containing the metal complexing agent TRIS (2-amino-2-hydroxy-methyl-1,3-propanediol) was an excellent... 

An alternative and often facile route to appropriately functionalised ICPs, that avoids the synthetic problems outlined in (ii) above, is the use of sulfonated species containing the desired molecular recognition/receptor site as the dopant anion for the conducting polymer chains. For example, calixarene-containing polypyrroles [34] and polyanilines [35] for selective metal ion detection have recently been prepared via the use of sulfonated calixarenes as dopant anions. We have similarly found that the incorporation of metal complexing agents such as sulfonated 8-hydroxyquinoline as dopants in polypyrroles provides a simple route to metal ion-selective ICPs [36]. 

Of course the reduction process also results in exclusion of small dopant anions from the polymer backbone. The dopants can be chosen so that the release process has the desired effect on the chemical composition of the immediate environment. For example. Miller described the triggered release of glutamate [59] and salicylate [60] amongst other compounds. In our own laboratories we have demonstrated the ability to release quinones [61] and metal complexing agents, dithiocarbamates (VII shown below) [62]. 

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