Difference Between Disodium EDTA and Tetrasodium EDTA

Main Difference – Disodium EDTA vs Tetrasodium EDTA

EDTA is a well-known chelating agent. It can bind with metal ions such as calcium and magnesium. EDTA cause “sequestration” of metal ions. This is done by binding with metal ions and forming a stable EDTA-metal complex. Disodium EDTA and tetrasodium EDTA are two forms of EDTA that are used in many industries. They are sodium salts of EDTA. Disodium EDTA has two sodium cations whereas tetrasodium EDTA has four sodium cations per molecule. The main difference between disodium EDTA and tetrasodium EDTA is that disodium EDTA has a pH lower than 7 whereas tetrasodium EDTA has a pH higher than 7.

Key Areas Covered

1. What is Disodium EDTA
      – Definition, Structure, Uses
2. What is Tetrasodium EDTA
      – Definition, Structure, Uses
3. What are the Similarities Between Disodium EDTA and Tetrasodium EDTA
      – Outline of Common Features
4. What is the Difference Between Disodium EDTA and Tetrasodium EDTA
      – Comparison of Key Differences

Key Terms: Disodium EDTA, EDTA, Edetate Disodium, Sodium Cation, Tetrasodium EDTA

What is Disodium EDTA

Disodium EDTA is a form of EDTA composed of two sodium cations. EDTA generally has four negatively charged oxygen atoms in its structure. In disodium EDTA, two of these oxygen atoms are combined with two sodium cations. Disodium EDTA is a byproduct of the synthesis of EDTA.  The synthesis of EDTA includes ethylenediamine, formaldehyde and sodium cyanide. Therefore, the sodium ions present in disodium EDTA comes from sodium cyanide.

Figure 1: The Chemical Structure of Disodium EDTA

The molecular formula of disodium EDTA is given as C₁₀H₁₄N₂Na₂O₈. The molar mass of this compound is about 336.2 g/mol. Disodium EDTA is called edetate disodium as well. It is a heavy metal chelating agent. This compound is available as a dry powder or in other solid forms. It appears as a white crystalline powder. The pH of the disodium EDTA solution may range from 4 to 6, but it does not exceed 7.

Disodium EDTA can be found in most of the products that we use in our day to day life. Some examples include shampoo, hair dyes, lotion, shower gel, etc. It is added to cosmetics in order to increase the shelf life of the product and to enhance the foaming properties. The role of disodium EDTA in medicine includes chelation therapy, anticoagulation, etc. Apart from that, this compound is used as a food additive as well.

However, there are some dangers regarding the applications of disodium EDTA in human care products. Since it is used in very little amounts in these products, it is not considered as a harmful ingredient. But since it facilitates skin penetration, the customers should also be aware of other ingredients present in our product.

What is Tetrasodium EDTA

Tetrasodium EDTA is a form of EDTA composed of four sodium cations. Since EDTA has four negatively charged oxygen atoms, all these oxygen atoms are bonded to sodium cations in tetrasodium EDTA compound. The molar mass of this compound is about 380.1 g/mol. The chemical formula of tetrasodium EDTA is C₁₀H₁₄N₂Na₄O₈. Tetrasodium EDTA is a byproduct of the synthesis of EDTA. 

Tetrasodium EDTA is available as dry powder, liquid form, etc. It appears as a colorless crystalline powder. Tetrasodium EDTA is water soluble. It is slightly soluble in ethanol. The pH of the tetrasodium EDTA solution ranges from 10 to 11.

The major applications of tetrasodium EDTA include its uses as a water softener and as a preservative. This compound is used in personal care products and cosmetics. This ingredient is added due to its ability to sequester metal ions. This sequestration results in increased shelf lives because tetrasodium EDTA can bind with metal ions to prevent them from reacting with other ingredients of the product.

Figure 2: Tetrasodium EDTA is an Ingredient in Many Cosmetics

However, Tetrasodium EDTA is considered as a low to moderate hazardous compound depending on its usage. Its effects can cause skin irritations and toxicity. Most importantly, Tetrasodium EDTA is recognized as an ecotoxin (it is harmful to the environment).

Similarities Between Disodium EDTA and Tetrasodium EDTA

• Both compounds are byproducts of EDTA synthesis process.
• Both compounds are sodium salts of EDTA.
• Both compounds can act as water softeners and preservatives.
• Both compounds are used as ingredients for personal care products and cosmetics.

Difference Between Disodium EDTA and Tetrasodium EDTA

Definition

Disodium EDTA: Disodium EDTA is a form of EDTA composed of two sodium cations.

Tetrasodium EDTA: Tetrasodium EDTA is a form of EDTA composed of four sodium cations.

Chemical Formula

Disodium EDTA: The chemical formula of disodium EDTA is C₁₀H₁₄N₂Na₂O₈.

Tetrasodium EDTA: The chemical formula of tetrasodium EDTA is C₁₀H₁₄N₂Na₄O₈.

Molar Mass

Disodium EDTA: The molar mass of disodium EDTA is about 336.2 g/mol.

Tetrasodium EDTA: The molar mass of tetrasodium EDTA is about 380.1 g/mol.

Normal pH

Disodium EDTA: The pH of disodium EDTA solution ranges from 4 to 6.

Tetrasodium EDTA: The pH of tetrasodium EDTA solution ranges from 10 to 11.

Conclusion

Disodium EDTA and tetrasodium EDTA are byproducts of EDTA synthesis process. They are sodium salts of EDTA. These compounds are used as preservatives in cosmetics and other human care products. The main difference between disodium EDTA and tetrasodium EDTA is that disodium EDTA has a pH lower than 7 whereas tetrasodium EDTA has a pH higher than 7.

References:

1. “Safety of Disodium EDTA.” LEAFtv,  Available here.
2. “Disodium EDTA.” Truth in Aging, Available here.
3. “EDTA tetrasodium.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, Available here.

Image Courtesy:

1. “Disodium EDTA” By Andel (talk) – Own work (Public Domain) via Commons Wikimedia
2. “1778608” (Public Domain) via Pixabay