Preparation EDTA Stock Solution

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Stock Solution Preparation Guide – EDTA

EDTA (EthyleneDiamineTetraAcetic acid) is a polyamino carboxylic acid widely used in molecular biology as a chelating agent. It sequesters divalent and trivalent metal ions such as Zn²⁺, Ca²⁺, and Fe³⁺, which are required cofactors for many enzymes, including DNases.

Common Commercial Forms of EDTA

• Anhydrous EDTA (Free Acid) – CAS 60-00-4, MW 292.24
• Disodium EDTA Dihydrate (EDTA·2Na·2H₂O) – CAS 6381-92-6, MW 372.24
• Tetrasodium EDTA Tetrahydrate (EDTA·4Na·4H₂O) – CAS 13235-36-4, MW 452.23

Solubility and Experimental Considerations

• Anhydrous EDTA (Free Acid)
  Has the lowest solubility in water. Dissolution requires the addition of a large amount of NaOH (approximately 3.1 molar equivalents) to raise the pH to 8.0.
• Disodium EDTA Dihydrate
  Has better solubility and is the most commonly used form for preparing 0.5 M EDTA stock solutions in molecular biology.next
• Tetrasodium EDTA
  Dissolves readily in water but results in a solution with pH > 10, making it unsuitable for most cell and molecular biology applications.

Available Reagents