Do I need a chelating agent

Hi!  As a standard we use 0.05% - 0.2%  Disodium EDTA in our products as a chelator.  We have a few products with no viscosity (room sprays and toners specifically) where we have noticed tiny pieces/floaties forming during the accelerated stability process.  We had the floaties analysed by a lab and they were found to be mainly copper and a small amount of tin.  Is it possible that the Disodium EDTA is causing this to precipitate out of the water?  We use De-ionized water - do we even need a chelator?


  • PharmaPharma Member, Pharmacist
    Copper and tin? How many ppm are we talking about? If one can see it, then I'd be concerned about the quality of the raw materials!
  • re: "We use De-ionized water - do we even need a chelator?"
    Yes, you do, because chelators not only bind metals but increase efficacy of preservatives. It's part of your preservation system.
    Disodium EDTA has very low solubility in water. I have to mix it for quite a while even at 0.1%. Not sure this is the very reason of your problem but as an option you can try Tetrasodium EDTA which solubilises easily and I noticed that suppliers advise using it for clear products.
  • ozgirlozgirl Member, PCF student
    I would be questioning where the Copper and Tin are coming from. What is in your formulation that could contain these metals as impurities?

    What is your pH? Metal ions can precipitate as hydroxides depending on the pH.

    You might get a better answer if you provide a list of the raw materials in your formula.
  • I could genuinely use an education here. Could someone help me understand how a chelating agent boosts preservative efficacy? Thanks!
  • chickenskinchickenskin Member
    edited September 2019


    Chelating agents (i.e., Na4EDTA) remove the cations and increase the permeability of the outer membrane to large hydrophobic molecules, antibiotics and preservatives.  This increase in antimicrobial activity produced by a chelating agent is known as permeabilization synergy and is the reason chelating agents are recommended for use with preservatives.

    Finnegan, Simon, and Steven L Percival. “EDTA: An Antimicrobial and Antibiofilm Agent for Use in Wound Care.” Advances in wound care vol. 4,7 (2015): 415-421. doi:10.1089/wound.2014.0577

  • Lucylu747Lucylu747 Member
    edited September 2019
    @ozgirl ; Formulation is as follows:

Sign In or Register to comment.