How to Prepare an EDTA Solution?

Ethylene diamine tetraacetic acid (EDTA) has several scientific and medicinal applications. It generates coordination complexes with metal ions, eliminating them on the chemical level. EDTA is used by biochemists to inactivate enzymes and by inorganic chemists as a chemical buffer. It is used by doctors to treat lead and calcium toxicity. It is also useful as a preservative in processed foods and cosmetics.

Preparing an EDTA solution can be difficult since it does not dissolve effectively at a pH of 7—the neutral pH of water. To make the solution, a strong base must be combined with water.

EDTA is used as a ligand and chelating agent. It’s particularly effective at capturing calcium (Ca²⁺) and iron (Fe³⁺) metal ions. The lab recipe for 0.5 M EDTA solution at pH 8.0 is given below.

EDTA Solution Reagents

Since the free form of EDTA is basically insoluble in water, the disodium EDTA is used to make an EDTA solution. Even so, the solid will not dissolve until the solution reaches pH 8.0, hence sodium hydroxide pellets or stock solution are required. To manufacture 0.5M EDTA stock solution, you will need the following ingredients:

• 186.1 grams EDTA (2Na•2H₂O)
• 800 milliliters of distilled water
• Sodium Hydroxide (NaOH) solution or solid (i.e. to adjust pH)

Instruments Required to Prepare EDTA Solution

• Measuring cylinder
• Conical flask or beaker
• Magnetic stirrer
• pH meter
• Paper towels
• Pipettes/spatula

Procedure for Preparing EDTA Solution

• Step 1: Stir 186.1 g of disodium ethylenediaminetetraacetate• 2H₂O in 800 ml of distilled water.
• Step 2: Using a magnetic stirrer, quickly swirl the solution.
• Step 3: Using NaOH, adjust the pH to 8.0. The amount of sodium hydroxide necessary to raise pH levels to the point where EDTA dissolves is going to surprise you. If you want to employ the solid NaOH pellets, you will require 18 to 20 grams of NaOH. To avoid overshooting the pH, gradually add the remaining NaOH. You may like to go from solid NaOH to a solution at the end for greater control. As the pH approaches 8.0, the EDTA begins to dissolve gradually.
• Step 4: Distilled water should be used to dilute the solution to 1 L.
• Step 5: Use a 0.5-micron filter to filter the solution.
• Step 6: As needed, dispense into containers and sanitize in an autoclave.
• Step 7: The end outcome should be colorless and opaque.
• Step 8: A 0.5M EDTA solution is stable for a year when maintained at 4°C.

Different Common EDTA Recipes

Making a stock solution has the benefit that it may be diluted to create additional solutions. But if you often utilize a certain concentration, you can just create it. The steps are the same. Disodium EDTA is combined with water, NaOH is used to dissolve it, and the distilled water is added to attain the desired volume.

0.2 M EDTA

• 74.45 g disodium EDTA
• 1 liter water
• NaOH pellets or solution

0.1 M EDTA

• 37.2 g disodium EDTA
• 1 liter water
• NaOH

100 mL 0.5M EDTA

• 18.61 g disodium EDTA
• 100 mL water
• NaOH

Video Reference

References

• https://sciencing.com/make-edta-solution-6452756.html
• https://www.thoughtco.com/0-5m-edta-solution-recipe-608140
• https://sciencenotes.org/how-to-make-edta-solution/
• https://sharebiology.com/preparation-of-edta-solution/