Complexes chelating agents

Ability to make metal complexes Chelating agents Immobilized metal chelate adsorption... 

Complexing chelating) agents citric acid, tartaric acid, B sodium tartrate), kerosene, segesterene, sodium citrate, oxalic acid, sodium oxalate, or orthophosphoric acid X... 

H02CCH2)2N-CH2 CH2-N(CH2C02H)2-An important compound, which owes its use to its sequestering properties. A multidentate chelating agent. Forms complexes with most elements. 

Liquid-liquid extractions using ammonium pyrrolidine dithiocarbamate (APDC) as a metal chelating agent are commonly encountered in the analysis of metal ions in aqueous samples. The sample and APDC are mixed together, and the resulting metal-ligand complexes are extracted into methyl isobutyl ketone before analysis. 

Generally, soluble materials are more effective as micronutrient sources than are insoluble ones. For this reason, many soil minerals that contain the micronutrient elements are ineffective sources for plants. Some principal micronutrient sources and uses are summarized below. In this discussion the term frits refers to a fused, pulverized siUceous material manufactured and marketed commercially for incorporation in fertilizers. Chelates refers to metaHoorganic complexes specially prepared and marketed as especially soluble, highly assimilable sources of micronutrient elements (see CHELATING agents). 

Certain compounds, known as chelating agents (qv), react synergisticaHy with many antioxidants. It is beheved that these compounds improve the functional abiUties of antioxidants by complexing the metal ions that often initiate free-radical formation. Citric acid and ethylenediaminetetraacetic acid [60-00-4] (EDTA), C2QH2gN20g, are the most common chelating agents used (22). 

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... 

For thermodynamic (stabiUty constants) and kinetic data involving crown-type inclusion complexes see References r38 and r39 stmctural results in References r40—r42 (see also Chelating agents). 

The lanthanides form many compounds with organic ligands. Some of these compounds ate water-soluble, others oil-soluble. Water-soluble compounds have been used extensively for rare-earth separation by ion exchange (qv), for example, complexes form with citric acid, ethylenediaminetetraacetic acid (EDTA), and hydroxyethylethylenediaminetriacetic acid (HEEDTA) (see Chelating agents). The complex formation is pH-dependent. Oil-soluble compounds ate used extensively in the industrial separation of rate earths by tiquid—tiquid extraction. The preferred extractants ate catboxyhc acids, otganophosphoms acids and esters, and tetraaLkylammonium salts. 

Platinum-group metals (qv) form complexes with chelating polymers with various 8-mercaptoquinoline [491-33-8] derivatives (83) (see Chelating agents). Hydroxy-substituted quinolines have been incorporated in phenol—formaldehyde resins (84). Stannic chloride catalyzes the condensation of bis(chloromethyl)benzene with quinoline (85). 

Metal Deactivation. Compounds capable of forming coordination complexes with metal ions are needed for this purpose. A chelating agent such as ethylene-diaminetetraacetic acid (EDTA) is a good example. 

Capillary Electrophoresis. Capillary electrophoresis (ce) is an analytical technique that can achieve rapid high resolution separation of water-soluble components present in small sample volumes. The separations are generally based on the principle of electrically driven ions in solution. Selectivity can be varied by the alteration of pH, ionic strength, electrolyte composition, or by incorporation of additives. Typical examples of additives include organic solvents, surfactants (qv), and complexation agents (see Chelating agents). 

Other complexing agents sometimes advocated are cryptates, especially the compound dubbed [2.2.2] (Kryptofix 222) [23978-09-8] (see Chelating agents). Crown ethers were originally advocated for reactions in the presence of soHd reagents (Uquid-soHd PTC). It is now known, however, that onium salts are equally suitable in many cases. 

Table 1 Hsts a number of chelating agents, grouped according to recognized stmctural classes. Because systematic nomenclature of chelating agents is frequently cumbersome, chelants are commonly referred to by common names and abbreviations. For the macrocyclic complexing agents, special systems of abbreviated nomenclature have been devised and are widely used. Some of the donor atoms involved ia chelation and the many forms ia which they can occur have been reviewed (5).

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