Gluconolactone & Sodium Benzoate/Geogard Ultra

I received a sample of GSB for testing, which I've been using at 1.5% for a shampoo formula. This formula is normally clear, but when I use GSB, it comes out opaque. There isn't any phase separation or precipitation, so it looks relatively stable, but I'd prefer if it were clear. After some trial and error, it appears to be a solubility issue. I've noticed that the formula is clear up until the point I add salt for thickening (1-2%). Normally, this formula readily accepts salt for thickening, but not in the presence of GSB. Any thoughts as to what I can do to clarify the solution? General process is as follows:

1. Under agitation (magnetic stirrer), slowly add cationic guar to water
2. Adjust pH to 3.5-5 with citric acid
3. Continue mixing for ~15 minutes
4. While mixing, add GSB to water
5. Heat solution to 60-65C
6. Add anionic surfactants, mix
7. Add other surfactants, mix
8. Add other non heat sensitive ingredients, mix
9. Allow to cool to <50C
10. Add cool-down phase ingredients (fragrance), mix
11. Adjust pH with citric acid to ~5.4
12. Add salt for thickening <-- product becomes opaque w/GSB

Comments

  • PerryPerry Administrator, Professional Chemist
    Strange.  What other ingredients are in the formula?  Since GSB is soluble in water there must be some other ingredient that is being kicked out of solution.
  • Surfactants are a sulfate-free blend at 15% ASM. The only notable ingredient there is Colonial Chemical SugaQuat TM-8610, which I believe is cationic, but supposedly is OK with anionics, non-ionics, and cationics. 

    Other ingredients:
    Panthenol 0.5%
    Glycerin 1%
    Essential Oils 0.4%
    Aloe vera juice (water replacement)
    Trisodium Ethylenediamine Disuccinate 0.3%
    Cationic guar 0.1%


  • MarkBroussardMarkBroussard Member, Professional Chemist
    GSB has a tendency to crystallize out of solution if you don't really pound it in first.  You might try adding GSB to water with no other ingredients, heat to 70C with homogenization, then add the other ingredients.

    But, the simpler approach would be to use a different preservative.
    Chemist/Microbiologist formulating in the Organic & Naturals arena under ECOCert/Natural Products Assn/Whole Foods/National Organic Program guidelines focused skincare & haircare products. 

    See website for details www.desertinbloomcosmeticslab.com
  • @MarkBroussard The challenge for me is that I'm supposed to mix cationic guar in room temperature water by itself. So to do what you suggest, my procedure would have to look something like:

    1. While mixing (high shear), add GSB to water
    2. Heat solution to 70C
    3. Remove from heat and allow to cool to RT
    Under agitation (magnetic stirrer), slowly add cationic guar to water
    4. Adjust pH to 3.5-5 with citric acid
    5. Continue mixing for ~15 minutes
    6. Heat solution to 50C
    7. Add anionic surfactants, mix
    8. Add other surfactants, mix
    9. Add other non heat sensitive ingredients, mix
    10. Allow to cool to <50C
    11. Add cool-down phase ingredients (fragrance), mix
    12. Adjust pH with citric acid to ~5.4
    13. Add salt for thickening

    As you can see, it's pretty complex, and I'd waste a lot of time heating, cooling, and heating again. I might try skipping step 3 and see what happens. That would save time and make this a lot easier. Do I need to hold at 70C? Is homogenization/high shear necessary or is mixing (w/magnetic stirrer) adequate?

    Thanks for your help.

  • MarkBroussardMarkBroussard Member, Professional Chemist
    For GSB, you really need to use a homogenizer at 70C to get it to stay in solution.  This preservative is much easier to work with in creams and lotions.

    I think you're getting hung up on using a particular ingredient as opposed to moving on taking the path of least resistance with an equally effective preservative that is much simpler to use.

    I honestly doubt whether the Guar cares much if you add it to 70C water or room temperature water and heat it up.  You might be better off if you make a slurry of Guar in Glycerin to pre-hydrate and add that slurry to the heated water phase.
    Chemist/Microbiologist formulating in the Organic & Naturals arena under ECOCert/Natural Products Assn/Whole Foods/National Organic Program guidelines focused skincare & haircare products. 

    See website for details www.desertinbloomcosmeticslab.com
  • @MarkBroussard OK, I give it a shot with my Silverson. If that doesn't do it, I don't know what will. I'm waiting for a sample of Euxyl PE 9010, so I may as well try to make the GSB work. If it doesn't, hopefully I'll have better luck with the Euxyl. Thanks again.
  • @thebrain ;
     this is what my supplier gave me as instructions

    1.       Use 2%

    2.       Add 2% to 20% water at 40C

    3.       Star stirring, it won’t dissolve until you adjust the pH

    4.       Adjust the pH to 7-7.25. You’ll notice that it dissolves and you get a clear solution

    5.       Add to the bulk of your formulation (you don’t want to add the 2% to your bulk because then you have to heat the whole bulk up to 40C and that’s a massive time/energy waster)

    6.       Adjust the pH of the bulk to 4.75 – 5.25

     

    IF you have problems with the pH drifting over a long period of time, I would suggested you add 3% sodium citrate to step 2 (in addition to the 2% Geo Ultra and 20% water).


    maybe this will help? 

  • Unknown Member

    When I use GSB with sodium citrate , after period of 1 week I expect white unsoluble flakes in the formula. I find the mechanism of polymerisation of gluconolactone with citric acid. Now I avoid the usin of this chemicals together.

    The problem of flakes disolved, but I still have a problem of precipitation(reversible) of GSB after number of days, even when GBS is single chemical in solution

  • We have had no problems with it when added in the beginning to water with either glycerin and/or propanediol.Ph as I am sure you have seen drops o/n to 5
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