Home Cosmetic Science Talk Formulating Iso-electric point of allantoin

  • Iso-electric point of allantoin

    Posted by doreen on December 17, 2018 at 10:43 am

    Can someone tell me the iso-electric point of allantoin? Or where to find it or how to calculate it?
    (I want to know for sure from which pH I can use it together with anionic substances.)

    Thanks! :+1:

    doreen replied 5 years, 3 months ago 3 Members · 6 Replies
  • 6 Replies
  • oldperry

    Member
    December 18, 2018 at 8:07 pm

    According to Merck, the following is true of a 5% solution in water:

    pH = 4.5 - 6 (5% in water, 20 deg C)

    https://pubchem.ncbi.nlm.nih.gov/compound/allantoin#section=Vapor-Pressure

  • doreen

    Member
    December 19, 2018 at 8:50 am

    @Perry
    So allantoin has a neutral charge between pH 4.5 and 6, below 4.5 cationic and above 6 anionic?
    Edit: Would it be very different if the concentration decreases to 0.5%, or lower?

    Thanks so much, Perry! :+1: :smiley:

  • Sibech

    Member
    December 19, 2018 at 9:14 am

    @Doreen at 25 degrees C It is probably the same as the solubility is about 0.6% in water.

  • doreen

    Member
    December 19, 2018 at 9:18 am

    @Sibech
    Ok, thanks a lot!!

  • oldperry

    Member
    December 19, 2018 at 1:37 pm

    @Doreen - well not exactly. I believe it is a weak acid so it wouldn’t be correct to claim it’s ever cationic. It either has a negative charged ion at lower pHs or it is neutral. See the structure of allantoic acid.

  • doreen

    Member
    December 19, 2018 at 4:01 pm

    @Perry
    You’re right! I thought it had a negative charge at higher pH’s.
    ( Ingredients To Die For is also mistaken I see: ‘Allantoin is an amphoteric compound that is anionic under basic conditions.’)
    Thanks for clearing that up! Now I know I never have to worry combining it with anionics.
    Thanks!!

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