Chelating agents steps

In the most common method for chemiluminescent immunoassay (GLIA), after the immunological reaction and any necessary separation steps, the labeled compounds or complexes react with an oxidizer, eg, hydrogen peroxide, and an enzyme, eg, peroxidase, or a chelating agent such as hemin or metal... 

DispEcement. In many of the appHcations of chelating agents, the overall effect appears to be a displacement reaction, although the mechanism probably comprises dissociations and recombinations. The basis for many analytical titrations is the displacement of hydrogen ions by a metal, and the displacement of metal by hydrogen ions or other metal ions is a step in metal recovery processes. Some analytical pM indicators function by changing color as one chelant is displaced from its metal by another. 

FIGURE 3-16 Accumulation and stripping steps in adsorptive stripping measurements of a metal ion (M I+) in the presence of an appropriate chelating agent (L). 

In order to suppress interferences due to the presence of inorganic species and reliably determine the proteinaceous composition of the sample, a clean-up step has often been introduced in the analytical procedure. This step may include the extraction of the proteinaceous matter by an ammonia solution [8], the use of a cation-exchange resin [8,55], a chelating agent [9,41,44], the use of a Cig resin or the use of barium chloride solution to suppress sulfates [10,81,82]. Table 9.1 reports the methods used to overcome such problems. 

In the case of mordenite, aluminum was solubilized in the two-step process primarily with mineral acids (5), while in the case of Y zeolites it involved acids (28,29), bases (17) or salts (30,31). The use of chelating agents has also been reported (32). 

There is no reason to believe that replacement of water by the donor groups of a chelating agent is fundamentally different from replacement when only unidentate ligands are involved. However, the multiplicity of steps may increase the difficulty in understanding the detailed mechanism, and mainly for this reason the simpler bidentate ligands have been most studied. 

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