0.5M EDTA Solution Recipe

Recipe for 0.5M EDTA at pH 8.0

EDTA (ethylenediaminetetraacetic acid) complexing agent molecule, shown bound to an iron ion.
EDTA (ethylenediaminetetraacetic acid) complexing agent molecule, shown bound to an iron ion. MOLEKUUL/SCIENCE PHOTO LIBRARY / Getty Images

Ethylenediaminetetraacetic acid (EDTA) is used as a ligand and chelating agent. It's especially useful for sequestering calcium (Ca2+) and iron (Fe3+) metal ions. This is the lab recipe for 0.5 M EDTA solution at pH 8.0:

EDTA Solution Materials

  • 186.1 grams EDTA (disodium ethylenediamine tetraacetate•2H2O) 
  • 800 milliliters distilled water
  • sodium hydroxide (NaOH) solution or solid (to adjust pH)

Procedure

  1. Stir 186.1g disodium ethylenediamine tetraacetate•2H2O into 800 ml of distilled water.
  1. Stir the solution vigorously using a magnetic stirrer.
  2. Add NaOH solution to adjust the pH to 8.0. If you use solid NaOH pellets, you'll need about 18-20 grams of NaOH. Add the last of the NaOH slowly so that you don't overshoot the pH. You may wish to switch from solid NaOH to a solution toward the end, for more precise control. The EDTA will slowly go into solution as the pH of the solution nears 8.0.
  3. Dilute the solution to 1 L with distilled water.
  4. Filter the solution through a 0.5 micron filter.
  5. Dispense into containers as needed and sterilize in an autoclave.

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