Chelates and chelating agents

Amperometric titrations involving chelates and chelating agents. J. Dolezal, K. Stulik and J. Zyka, Chelates Anal. Chem., 1972, 3, 57-150 (300). 

Chelates and chelating agents in the analytical chemistry of niobium and tantalum. E. Lassner and R. Puschel, Chelates Anal. Chem., 1969, 2, 213-340 (311). 

Conductometric and high frequency impedimetric titrations involving chelates and chelating agents. 

R. Piischel and E. Lassner, Chelates and Chelating Agents in the Analytical Chemistry of Molybdenum and Tungsten, in Chelates in Analytical Chemistry, Vol. 1 (H. A. Flaschka and A. J. Barnard, eds.), Marcel Dekker, New York (1967). 

In 1955 Mellor was appointed Professor of Chemistry at the Univeraty of New South Wales. Unfortunately, he did no more experimental research, but he was the author of four books The Rdle of Science and Industry in Australia in the War of 1939-194509), Chelating Agents and Metal Chelates 20),The Evolution of the Atomic Theory (21), and Chemistry of Chelation and Chelating Agents (22). 

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. 

Cupferron is a ligand whose strong affinity for metal ions makes it useful as a chelating agent in liquid-liquid extractions. The following distribution ratios are known for the extraction of Hg +, Pb +, and Zn + from aqueous solutions to an organic solvent. 

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). 

Many excellent chelating agents are piepaied by the reaction of sahcylaldehyde with 1,2- or 1,3-dianiinoalkanes and have wide use in chemistry, for... 

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. 

Mineral oil and paraffins should not be used, because these are not metabolized and may irritate tissue. Various other additives are needed for stabiUty, stefihty, and isotonicity antimicrobial preservatives, antioxidants (qv), chelating agents (qv), and buffers. No parenteral container material is completely inert to parenteral solvent systems. 

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