Chelating Agent

<p ><b>Chelation</b> is the formation or presence of two or more separate <a href="http://en.wikipedia.org/wiki/Coordinate_bond" title="Coordinate bond" class="mw-redirect" >coordinate bonds</a> between a <a href="http://en.wikipedia.org/wiki/Denticity" title="Denticity" >polydentate</a> (multiple bonded) <a href="http://en.wikipedia.org/wiki/Ligand" title="Ligand" >ligand</a> and a single central atom.<sup id="cite_ref-IUPAC_0-0" class="reference" ><a href="http://en.wikipedia.org/wiki/Chelating_agent#cite_note-IUPAC-0" >[1]</a></sup> Usually these <a href="http://en.wikipedia.org/wiki/Ligand" title="Ligand" >ligands</a> are <a href="http://en.wikipedia.org/wiki/Organic_compound" title="Organic compound" >organic compounds</a>, and are called chelants, chelators, chelating agents, or sequestering agents.

The ligand forms a <b>chelate complex</b> with the substrate. Chelate complexes are contrasted with <a href="http://en.wikipedia.org/wiki/Coordination_complex" title="Coordination complex" >coordination complexes</a> composed of<a href="http://en.wikipedia.org/wiki/Denticity" title="Denticity" >monodentate ligands</a>, which form only one bond with the central atom.

Chelants, according to <a href="http://en.wikipedia.org/wiki/ASTM" title="ASTM" class="mw-redirect" >ASTM</a>-A-380, are "chemicals that form soluble, complex molecules with certain metal ions, inactivating the ions so that they cannot normally react with other elements or ions to produce precipitates or scale."

The word chelation is derived from <a href="http://en.wikipedia.org/wiki/Greek_language" title="Greek language" >Greek</a> χηλή, <i>chelè</i>, meaning claw; the ligands lie around the central atom like the claws of a <a href="http://en.wikipedia.org/wiki/Lobster" title="Lobster" >lobster</a>.<sup id="cite_ref-1" class="reference" ><a href="http://en.wikipedia.org/wiki/Chelating_agent#cite_note-1" >[2]</a></sup>

<h3 >Nutritional supplements</h3>

<p >In the 1960's, scientists developed the concept of chelating a metal ion prior to feeding the element to the animal. They believed that this would create a neutral compound, protecting the mineral from being complexed with insoluble salts within the stomach, rendering the metal unavailable for absorption. Amino acids, being effective metal binders, were chosen as the prospective ligands, and research was conducted on the metal-amino acid combinations. The research supported that the metal-amino acid chelates were able to enhance mineral absorption.

During this period, synthetic chelates were also being developed. An example of such synthetics is ethylenediaminetetraacetic acid (EDTA). These synthetics applied the same concept of chelation and did create chelated compounds; however, these synthetics were too stable and not nutritionally viable. If the mineral was taken from the EDTA ligand, the ligand could not be used by the body and would be expelled. During the expulsion process the EDTA ligand will randomly chelate and strip another mineral from the body.<sup id="cite_ref-11" class="reference" ><a href="http://en.wikipedia.org/wiki/Chelating_agent#cite_note-11" >[12]</a></sup>

According to the Association of American Feed Control Officials (AAFCO), a metal amino acid chelate is defined as the product resulting from the reaction of a metal ion from a soluble metal salt with a mole ratio of one to three (preferably two) moles of amino acids. The average weight of the hydrolyzed amino acids must be approximately 150 and the resulting molecular weight of the chelate must not exceed 800 Da.

Since the early development of these compounds, much more research has been conducted, and has been applied to human nutrition products in a similar manner to the animal nutrition experiments that pioneered the technology. Ferrous bis-glycinate is an example of one of these compounds that has been developed for human nutrition. <sup id="cite_ref-12" class="reference" ><a href="http://en.wikipedia.org/wiki/Chelating_agent#cite_note-12" >[13]</a></sup></p>

<h3 >[<a href="http://en.wikipedia.org/w/index.php?title=Chelation&action=edit&section=7" title="Edit section: Fertilizers" >edit</a>]Fertilizers</h3>

<p >Many mineral deficiencies can occur in plants, such as iron chlorosis, which can reduce the nutritional benefits of crops and eventually result in plant death. Mineral chelates have been used to alleviate the mineral deficiencies of affected crops through liquid foliar applications. These fertilizers are also used to prevent deficiencies from occurring and improving the overall health of the plants. <sup id="cite_ref-13" class="reference" ><a href="http://en.wikipedia.org/wiki/Chelating_agent#cite_note-13" >[14]</a></sup></p>

<h3 >[<a href="http://en.wikipedia.org/w/index.php?title=Chelation&action=edit&section=8" title="Edit section: Heavy metal detoxification" >edit</a>]Heavy metal detoxification</h3>

<div class="rellink relarticle mainarticle" >Main article: <a href="http://en.wikipedia.org/wiki/Chelation_therapy" title="Chelation therapy" >Chelation therapy</a></div>

<p >Chelation therapy is the use of chelating agents to detoxify <a href="http://en.wikipedia.org/wiki/Poison" title="Poison" >poisonous</a> metal agents such as <a href="http://en.wikipedia.org/wiki/Mercury_poisoning" title="Mercury poisoning" >mercury</a>, <a href="http://en.wikipedia.org/wiki/Arsenic" title="Arsenic" >arsenic</a>, and <a href="http://en.wikipedia.org/wiki/Lead" title="Lead" >lead</a> by converting them to a chemically inert form that can be excreted without further interaction with the body, and was approved by the <a href="http://en.wikipedia.org/wiki/U.S._Food_and_Drug_Administration" title="U.S. Food and Drug Administration" class="mw-redirect" >U.S. Food and Drug Administration</a> in 1991. In <a href="http://en.wikipedia.org/wiki/Alternative_medicine" title="Alternative medicine" >alternative medicine</a>, chelation is used as a <a href="http://en.wikipedia.org/wiki/Autism_therapies#Chelation_therapy" title="Autism therapies" >treatment</a> for<a href="http://en.wikipedia.org/wiki/Autism" title="Autism" >autism</a>, although this practice is controversial due to the absence of scientific plausibility, lack of FDA approval, and its potentially deadly side-effects.<sup id="cite_ref-14" class="reference" ><a href="http://en.wikipedia.org/wiki/Chelating_agent#cite_note-14" >[15]</a></sup>

Although they can be beneficial in cases of heavy metal poisoning, chelating agents can also be dangerous. Use of disodium EDTA instead of calcium EDTA has resulted in fatalities due to <a href="http://en.wikipedia.org/wiki/Hypocalcemia" title="Hypocalcemia" class="mw-redirect" >hypocalcemia</a>.<sup id="cite_ref-15" class="reference" ><a href="http://en.wikipedia.org/wiki/Chelating_agent#cite_note-15" >[16]</a></sup></p>

<h3 >[<a href="http://en.wikipedia.org/w/index.php?title=Chelation&action=edit&section=9" title="Edit section: Other medical applications" >edit</a>]Other medical applications</h3>

<p ><a href="http://en.wikipedia.org/wiki/Antibiotic" title="Antibiotic" class="mw-redirect" >Antibiotic</a> <a href="http://en.wikipedia.org/wiki/Medication" title="Medication" class="mw-redirect" >drugs</a> of the <a href="http://en.wikipedia.org/wiki/Tetracycline" title="Tetracycline" >tetracycline</a> family are chelators of <a href="http://en.wikipedia.org/wiki/Calcium" title="Calcium" >Ca</a><sup >2+</sup> and <a href="http://en.wikipedia.org/wiki/Magnesium" title="Magnesium" >Mg</a><sup >2+</sup> ions.

EDTA is also used in <a href="http://en.wikipedia.org/wiki/Endodontic_therapy" title="Endodontic therapy" >root canal treatment</a> as a way to irrigate the canal. EDTA softens the dentin facilitating access to the entire canal length and to remove the smear layer formed during instrumentation.

Chelate complexes of <a href="http://en.wikipedia.org/wiki/Gadolinium" title="Gadolinium" >gadolinium</a> are often used as <a href="http://en.wikipedia.org/wiki/Contrast_medium" title="Contrast medium" >contrast agents</a> in <a href="http://en.wikipedia.org/wiki/MRI" title="MRI" class="mw-redirect" >MRI scans</a>.</p>

<h3 >[<a href="http://en.wikipedia.org/w/index.php?title=Chelation&action=edit&section=10" title="Edit section: Chemical applications" >edit</a>]Chemical applications</h3>

<p ><a href="http://en.wikipedia.org/wiki/Homogeneous_catalyst" title="Homogeneous catalyst" class="mw-redirect" >Homogeneous catalysts</a> are often chelated complexes. A typical example is the <a href="http://en.wikipedia.org/w/index.php?title=Ruthenium(II)_chloride&action=edit&redlink=1" class="new" title="Ruthenium(II) chloride (page does not exist)" >ruthenium(II) chloride</a> chelated with <a href="http://en.wikipedia.org/wiki/BINAP" title="BINAP" >BINAP</a> (a bidentate <a href="http://en.wikipedia.org/wiki/Phosphine" title="Phosphine" >phosphine</a>) used in e.g. <a href="http://en.wikipedia.org/wiki/Noyori_asymmetric_hydrogenation" title="Noyori asymmetric hydrogenation" >Noyori asymmetric hydrogenation</a> and asymmetric isomerization. The latter has the practical use of manufacture of synthetic <a href="http://en.wikipedia.org/wiki/Menthol" title="Menthol" >(–)-menthol</a>.

<a href="http://en.wikipedia.org/wiki/Citric_acid" title="Citric acid" >Citric acid</a> is used to <a href="http://en.wikipedia.org/wiki/Citric_acid#Water_softening" title="Citric acid" >soften water</a> in <a href="http://en.wikipedia.org/wiki/Soap" title="Soap" >soaps</a> and laundry <a href="http://en.wikipedia.org/wiki/Detergent" title="Detergent" >detergents</a>. A common synthetic chelator is <a href="http://en.wikipedia.org/wiki/EDTA" title="EDTA" class="mw-redirect" >EDTA</a>. <a href="http://en.wikipedia.org/wiki/Phosphonate" title="Phosphonate" >Phosphonates</a> are also well known chelating agents. Chelators are used in water treatment programs and specifically in <a href="http://en.wikipedia.org/w/index.php?title=Steam_engineering&action=edit&redlink=1" class="new" title="Steam engineering (page does not exist)" >steam engineering</a>, e.g., <a href="http://en.wikipedia.org/w/index.php?title=Boiler_water_treatment_system&action=edit&redlink=1" class="new" title="Boiler water treatment system (page does not exist)" >boiler water treatment system</a>: <i>Chelant Water Treatment system.</i>

Products such as Bio-Rust and Evapo-Rust are chelating agents sold for the removal of rust from iron and steel.</p>

Chelating Agent

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