What are Chelating Agents?

Ann Louise Truschel

Chelating agents are chemicals or chemical compounds that react with heavy metals, rearranging their chemical composition and improving their general stability and likelihood of bonding with other metals, nutrients, or substances. When this happens the metal that remains is known as a “chelate,” a word that derives from the Greek chela, meaning claw. These sorts of agents exist in nature and are an important part of many biological processes. They help transport nutrients throughout plants, for instance, and assist in digestion in people and many animals. In many places they’re also created synthetically, and have a number of important uses in both industry and medicine. These sorts of agents can be very useful any time heavy metal ions need to be broken down, isolated, or moved.

Chelating agents that exist in nature aid in digestion.
Chelating agents that exist in nature aid in digestion.

How They Work

The chemistry behind how these agents work tends to be somewhat complex, but to put it simply they bond to metal ions in such a way as to reorganize their core structure and chemical composition. Most metals have chemical structures that most closely resemble chains, but chelating agents join the ends in order to form a ring, known as a ligand. This ring structure makes the ions more stable and helps them move with greater ease through a range of different environments.

The cleaning power of detergents is enhanced with chelating agents.
The cleaning power of detergents is enhanced with chelating agents.

Ethylenediamine is one of the most common chelating agents, and is a good example of how these substances work. It has a chemical structure of C2H8N2. It is known chemically as a multidentate agent, or more specifically a bidentate ligand, which means that can form two bonds — each nitrogen atom can bond with the same metal ion. Depending on how many bonds the metal ion can accept, the ion may form a chelate with one, two, or three ethylenediamine molecules. The more bonds there are, the stronger and more stable the chelate is likely to be.

Chelating agents are used to reduce food spoilage.
Chelating agents are used to reduce food spoilage.

Role in Nature

Naturally-occurring chelates are necessary for many life-sustaining processes, and they can’t be formed without agents that can help their transformation. The vitamin B12-cobalt complex is one example. It is a dietary requirement for people and most animals, but in most cases it can’t properly be digested or absorbed until it has formed a ligand with one of the many chelating agents in the body. The hemoglobin-iron complex transports oxygen through the blood after chelation, and similarly, the chlorophyll-magnesium complex is a critical component of photosynthesis in plants. If chelating agents weren’t at work these processes would be slower, and might not even happen at all.

Use in Industry

Agents are commonly used in industrial manufacturing as detergent additives, stabilizing agents, preservatives, and flavor and color retainers. Ethylenediaminetetraacetic acid (EDTA) is one of the most popular. It is what is known as a “quadridentate” or “hexadentate” agent that is capable of forming either four or six bonds with metal ions. EDTA is widely used for enhancing the cleaning power of detergents and soaps by forming chelates with the magnesium and calcium metals in hard water. These agents are also used as color retainers for textile dyes.

EDTA is used in many places as a food additive, too. Food spoilage is typically catalyzed by enzymes that require certain transition metals in order to work, but EDTA deactivates the spoilage enzymes that would otherwise cause the food to become rancid. It also deactivates the enzymes that cause food to lose color or flavor.

Importance to Medicine

These agents are essential to many medical treatments and tests. They can be used to isolate and move calcium ions out of the blood, which helps preserve blood during surgeries or operations, for instance, and they’re also an important part of many lead poisoning and other metal poisoning treatments. When agents enter the bloodstream they can target free metal ions and chelate them and then remove them from the blood stream, often by flushing them out in urine. Dimercaprol is one of the most common examples. It removes heavy metal poisons, such as antimony, mercury, and arsenic, by forming sulfur bonds to the metal ions.

Checking for lead in the body is a common hematology test for children.
Checking for lead in the body is a common hematology test for children.

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Discussion Comments


I run a maid service and worry about chelating agents in the cleaners I use on natural stone counters, showers, walls and floors. I want to start using Young Living's Thieves cleaner, but am worried that it contains some chelating agents. Does anyone know anything about this product that can advise me on its use. Thanks Debra


@MissDaphne: Chelating agents can bond to heavy metals and create more space for them to bond so that they can become complex ions. The absorption of metals is limited by when they form insoluble products, but when they become complex ions they can remain in the solution without precipitating for longer, increasing the absorption of these metals.


I never saw the House episode. Manganese toxicity was from an aquarium rare earth product. Welders often get it. My guess is most people die early because of mineral water and too many minerals in foods. Cereals are full of dangerous minerals. Multivitamins would kill me if I took one for twenty days. I feel bad after two multivitamins.


Hey, good question. It's actually in the last paragraph of the article--it says they use EDTA for that. The Wikipedia article says they use something called DMSA, though. But I wonder if much heavy metal poisoning takes place in real life, as opposed to on House!

I like that show, too, and now I get to know the chemistry involved! I knew so little about it, I thought the docs on the show were talking about "kelation" therapy. Oops!


I'm a big fan of the TV House on Fox and sometimes when they think a person has heavy metal poisoning, they use chelation treatment to remove the metal from the person's blood. Does chelation treatment of ? Or is done a totally different way?

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