Which of the following is an example of a chelating agent?

• A. Edetic acid
• B. Sodium benzoate
• C. Calcium chloride
• D. Glycerin

Answer: (A)

A chelating agent binds metal ions through multiple donor atoms to form stable, ring-like complexes. Edetic acid, known as EDTA, is a classic example because it has several coordinating sites—the four carboxylate groups and two amine nitrogens—that can attach to a single metal ion, creating a hexadentate ligand. This strong, multidentate binding effectively sequesters metal ions such as calcium, magnesium, or iron, helping stabilize formulations and prevent metal-catalyzed reactions or oxidative processes. The other substances don’t act as chelating agents: sodium benzoate is mainly a preservative, calcium chloride is simply a source of calcium ions, and glycerin is a humectant/solvent with no significant metal-binding capability.