What are chelating agents ?
According to INCI (International Nomenclature for Cosmetic Ingredients), chelating agents are “ingredients that complex with and inactivate metallic ions to prevent their adverse effects on the stability or appearance of cosmetic products.” Simply put, chelating agents are compounds that bond to metal ions, rendering them inert and eliminating any negative effects they may produce. Once bonded to a chelating agent, the metal becomes chemically and biologically inactive. This keeps the product free of microbes by starving them of their metal supply and preventing them from reproducing. They are not preservatives, but instead work in tandem with preservatives to keep the products fresher for longer. All chelating compounds are organic, meaning they contain carbon, but only a few are made by plants. The rest are synthesized artificially in various chemical processes
How do chelating agents work?
Chelating agents work by forming one or more bonds to the free metal ion. These bonds are ionic – the strongest kind of bond – due to the difference in electronegativity between the ion and the chelating agent. Most of the time, the bonding atom is oxygen, sulfur, or phosphorus. Ligands are organic compounds that are bound to a metal. Ligands with one bond are monodentate, those with two bonds are bidentate, ones with three are tridentate, and those that have four or more are polydentate. Polydentate ligands are the most common and versatile. When a chelate bonds with a metal, it becomes known as a “coordination complex.” The word “chelate” is based on the greek word chelos, or claw. This is because chelating compounds are usually claw shaped. When they bond to a metal, they often appear to be grasping it in a claw-like manner. The bonds render the ion inert, so that it can no longer react with skin cells or chemicals. The bonds also make it soluble in water, so it can pass through cell walls via osmosis or dissolve in the bloodstream.
Why are chelating agents used in skincare products?
There are many ways that metal can enter cosmetics. These include water, production equipment, and impurities in ingredients. While small amounts of metal are safe, they can still cause damage to the products themselves and harm the skin in large quantities. Ions can impair foaming reactions, cause oxidation reactions, create rancidity and spoilage, degrade fragrance, and discolor the final product. Having a chelating agent also ensures that the ions won’t be around when the product is used. Some formulations don’t need chelating agents, but those that contain clay, botanical extracts, aloe vera, fruit powders, waxes, and thickening agents (among other things) do need them. The chelating agents also have moderate antimicrobial properties when combined with broad-spectrum preservatives.
What are some examples of Chelating agents
Almost all chelating agents are organic compounds, meaning that they contain multiple carbon atoms. Some are derived from plants and other living organisms while others are synthetically made. EDTA, scientifically known as ethylenediaminetetraacetic acid, is the most common chelating agent. It is a hexadentate ligand and is found in everything from shampoo to soda to household cleaners. Used in concentration of .05 to .2%, it is very cheap and effective across the spectrum. There are two forms. Disodium EDTA is meant for use in moderately acidic and neutral products while tetrasodium EDTA is better suited to more alkaline or basic formulations. However, it gets a bad rap due to the fact that it is derived from petroleum and is not completely green. It is not biodegradable, unlike other compounds. Citric acid is another chelating agent. Unlike EDTA, it is a biologically synthesized compound and found naturally in oranges, lemons, grapefruits, limes, and other citrus fruit. It is often used in shampoo to remove wax, dye, and chemical deposits from hair. By removing the metals from water, it also helps the foaming agents to do their work better. Sodium phytate is the sodium salt of phytic acid, which is biologically derived from corn phosphonates, the chemicals that plants use to store phosphate. It is a natural antioxidant and helps minimize free radical damage to the skin. Gluconolactone, also known as glucono delta lactone, is another chelating agent found naturally in the form of gluconic acid, which comes from royal jelly, wine, honey, fruit juices, and other fermented organic products. Aside from its moisturizing properties and ability to combat the effects of aging, gluconolactone serves as a chelating agent to increase the antimicrobial effects of most broad-spectrum preservatives. Etidronic acid is used in cleaning agents to minimize the effects of hard water and inhibit corrosion, while in cosmetics, it is used to suppress the formation of free radicals, as an emulsion stabilizer, and control viscosity. While it is safe to use, some experts recommend washing products that contain etidronic acid off completely after use. Phosphonates are a major category of chelating agents. They are derived from the compounds that plants use to store phosphates. Structurally similar to compounds such as EDTA, they are also very soluble in water. A notable subclass is the bisphosphonates, which differ in that they have two phosphonate groups instead of one.
Are chelating agents safe?
Yes. The main purpose of chelating agents is to render metals inert so that they cannot harm the body or the product. In fact, some chelating compounds are actually the active ingredients in medications used to treat poisoning! Most cosmetics, especially face washes, shampoos, soaps, and face masks, are meant to be washed off after use. This is to ensure that the skin is not over exfoliated or dried out by the formulations. Some chelating agents can be irritating to people with sensitive skin, so do research before purchasing to ensure that the product is compatible with your skin type. EDTA, one popular chelator, has come under fire for not being biodegradable and for being synthesized from fossil fuels. However, claims that it is a carcinogen have been disproved. When ingested in large quantities, EDTA can cause zinc deficiencies. However, cosmetics are not meant to be consumed, so this is not a problem.
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