Animal feed additives Synthetic chelates such as
ethylenediaminetetraacetic acid (EDTA) proved 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 randomly chelated and stripped other minerals from the body. 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 metal ions from a soluble metal salt with amino acids, with a
mole ratio in the range of 1–3 (preferably 2) moles of amino acids for one mole of metal. 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.
Dental use Dentin adhesives were first designed and produced in the 1950s based on a co-monomer chelate with calcium on the surface of the tooth and generated very weak water-resistant chemical bonding (2–3 MPa).
Chelation therapy Chelation therapy is an antidote for poisoning by
mercury,
arsenic, and
lead. Chelating agents convert these metal ions into a chemically and biochemically inert form that can be excreted. Chelation using
sodium calcium edetate has been approved by the
U.S. Food and Drug Administration (FDA) for serious cases of
lead poisoning. It is not approved for treating "
heavy metal toxicity". Although beneficial in cases of serious lead poisoning, use of disodium EDTA (edetate disodium) instead of calcium disodium EDTA has resulted in fatalities due to
hypocalcemia. Disodium EDTA is not approved by the FDA for any use,
Contrast agents Chelate complexes of
gadolinium are often used as
contrast agents in
MRI scans, although
iron particle and
manganese chelate complexes have also been explored. Bifunctional chelate complexes of
zirconium,
gallium,
fluorine,
copper,
yttrium,
bromine, or
iodine are often used for conjugation to
monoclonal antibodies for use in antibody-based
PET imaging. These chelate complexes often employ the usage of
hexadentate ligands such as
desferrioxamine B (DFO), according to Meijs
et al., and the gadolinium complexes often employ the usage of octadentate ligands such as DTPA, according to Desreux
et al.
Auranofin, a chelate complex of
gold, is used in the treatment of rheumatoid arthritis, and
penicillamine, which forms chelate complexes of
copper, is used in the treatment of
Wilson's disease and
cystinuria, as well as refractory rheumatoid arthritis.
Nutritional advantages and issues Chelation in the intestinal tract is a cause of numerous interactions between drugs and metal ions (also known as "
minerals" in nutrition). As examples,
antibiotic drugs of the
tetracycline and
quinolone families are chelators of
Fe2+,
Ca2+, and
Mg2+ ions. EDTA, which binds to calcium, is used to alleviate the
hypercalcemia that often results from
band keratopathy. The calcium may then be removed from the
cornea, allowing for some increase in clarity of vision for the patient.
Homogeneous catalysts are often chelated complexes. A representative example is the use of
BINAP (a bidentate
phosphine) in
Noyori asymmetric hydrogenation and asymmetric isomerization. The latter has the practical use of manufacture of synthetic
(–)-menthol.
Cleaning and water softening A chelating agent is the main component of some rust removal formulations.
Citric acid is used to
soften water in
soaps and laundry
detergents. A common synthetic chelator is
EDTA.
Phosphonates are also well-known chelating agents. Chelators are used in water treatment programs and specifically in
steam engineering. Although the treatment is often referred to as "softening", chelation has little effect on the water's mineral content, other than to make it soluble and lower the water's
pH level.
Fertilizers Metal chelate compounds are common components of fertilizers to provide micronutrients. These micronutrients (manganese, iron, zinc, copper) are required for the health of the plants. Most fertilizers contain phosphate salts that, in the absence of chelating agents, typically convert these metal ions into insoluble solids that are of no nutritional value to the plants.
EDTA is the typical chelating agent that keeps these metal ions in a soluble form.
Economic situation Because of their wide needs, the overall chelating agents growth was 4% annually during 2009–2014 and the trend is likely to increase.
Aminopolycarboxylic acids chelators are the most widely consumed chelating agents; however, the percentage of the greener alternative chelators in this category continues to grow. The consumption of traditional aminopolycarboxylates chelators, in particular the EDTA (
ethylenediaminetetraacetic acid) and NTA (
nitrilotriacetic acid), is declining (−6% annually), because of the persisting concerns over their toxicity and negative environmental impact. == Reversal ==