0.5 M EDTA Solution Recipe

Add the last of the NaOH slowly so that you don't overshoot the pH

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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:

Solution Materials

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

Procedure

  1. Stir 186.1 g disodium ethylenediaminetetraacetate•2H2O into 800 ml of distilled water.
  2. Stir the solution vigorously using a magnetic stirrer.
  3. Add NaOH solution to adjust the pH to 8.0. If you use solid NaOH pellets, you'll need 18 to 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 nears 8.0.
  4. Dilute the solution to 1 L with distilled water.
  5. Filter the solution through a 0.5-micron filter.
  6. Dispense into containers as needed and sterilize in an autoclave.

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