Acetic acid, ethylenediamine tetra complexes

The most widely used titrant for such determinations is diamino-ethane-tetra-acetic acid (ethylenediamine tetra-acetic acid) which is conveniently employed as the disodium salt, referred to throughout this book as EDTA. (The titrant is referred to in the B,P, and B,P,C, as sodium edetate, but this synonym has not gained universal acceptance.) Many other amino-polycarboxylic acids have been used and in certain special applications they may have some advantage for routine pharmaceutical work, however, it has not been found necessary to use any titrant other than EDTA. This substance reacts stoichiometrically with most metals to form a 1 1 complex and, usually, the reaction is instantaneous (but see Aluminium, p. 32). pH has a marked effect on the stability of the complexes formed the alkaline earth metals form complexes that are stable in alkaline solution but decompose in neutral and acid solution aluminium, copper, lead and mercury all complex under mildly acid conditions while bismuth and ferric iron form stable complexes in a solution as acid as pH 1. The monovalent ions of sodium, potassium and silver form complexes that are too weak to be used for titration purposes whilst mercurous mercury forms no complex,... 

A great number of ligands, such as the anions of ethylenediamine-NNN N -tetra-acetic acid (EDTA), described in detail by Schwarzen-bach and his school (29, 30), show a pronounced selectivity for alkaline earth and other metal cations (30). Because of the limited lipid solubility of these ligands and their complexes, such compounds are, however, not suited as ion carriers in lipophilic membranes (Fig. 2). The ability... 

Iron should be coordinated by the chelate in such a manner as to prevent direct access of oxygen and hydrogen peroxide. If this is achieved, then hydroxyl-radical production will be reduced to a minimum. Some iron complexes, for instance ethylenediamine tetra-acetic acid (EDTA) (Fig. 3a), generate hydroxyl radicals efficiently while others such as DFO and the hydroxypyridinones (Fig. 3b) do not. By designing chelators that produce extremely stable complexes, the generation of hydroxyl radicals is further minimized. Such stable complex formation would also reduce the tendency for iron redistribution within the body. 

Complex formation reactions, in which the reactants are combined to form a soluble ion or compound. The most important reagent for formation of such complexes is ethylenediamine tetra-acetic acid, EDTA (as the disodium salt). 

Numerous tertiary amines that also contain carboxylic acid groups form remarkably stable chelates with many metal ions. Ethylenediamine tetra-acetic acid (EDTA) can be used for determination of 40 elements by direct titration using metal-ion indicators for endpoint detection. Direct titration procedures are limited to metal ions that react rapidly with EDTA. Back titration procedures are useful for the analysis of cations that form very stable EDTA complexes and for which a satisfactory indicator is not available. EDTA is also used for determining water hardness the total concentration of calcium and magnesium expressed in terms of the calcium carbonate equivalent. 

Some TCA masks have been presented as chelated TCA. Chelation is a medical therapy that aims to detoxify the body of harmful minerals and metals. Chemically, chelation is the process by which an organic substance (the chelator) binds metal ions (iron, copper, lead, calcium, etc.) into inactive, non-toxic and water-soluble complexes that are easily eliminated in the urine. Intravenous chelation therapy (e.g. with ethylenediamine tetra acetic acid, EDTA) is often used to treat poisoning with heavy metals, including lead. The use of the term chelation therefore seems inappropriate as far as TCA is concerned, and has no chemical basis since TCA is not a metal. The little information available states that chelation reduces the speed of penetration of TCA and therefore its depth of action. Might what we call chelation be partial inactivation of the TCA The directions of use for Accu Peel state that a process called chelation allows the TCA to reach an even depth at the same time as using lower concentrations of TCA . Might chelation, on the contrary, be a process that activates the TCA But how can TCA be activated ... 

The retention profiles of the water-soluble polymer the poly (ethylenediamine tetra-acetic acid-co-lactose) clearly show that the polymer has a strong binding ability for iron and chromium, as it exhibited a strong metal complexation with Cr(III) and Fe(III) with retention values of 100%. In contrast, Co(II), Ni(II), Cu(II), Zn(II), Sr(III), Cd(II), Pb(II), and Al(III) showed lower retention values (20-80%). Thus, the enrichment of Cr(III) and Fe(III) from the other metal ions can be achieved. 

It is evident that if the amount of acid employed is below the stoichiometric ratio, the demineralization reaction will not be completed. The acid concentration and the reaction time depend on the source, but these parameters must be carefully controlled in order to minimize the hydrol3dic depolymerization and deacetylation of chitin. High temperature treatments must also be avoided to prevent thermal degradation [10]. An alternative treatment for demineralization makes use of the complexing agent EDTA (ethylenediamine tetra acetic acid) in basic media [15]. 

The formation of hydroxyl radicals (HO ) by the reaction of the Cu(II) complex of ethylenediamine tetra-acetic acid (EDTA) with H2O2 in the presence of biological reductants, such as L-ascorbic acid and l-cysteine, has been demonstrated by ESR spectroscopy using water-soluble spin-traps (Ozawa et al. 1992). 

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