Adjusting ph for carbomer gel with EDTA

Should be easy enough question . EDTA  %1 aprox ph of 10 but this is point when most carbomers fall out to liquid . Need to drop to 6-6.5 s to keep thick .

 used  potassium sorbate  but I understand its not effective over phof 6.5?  (I assume thats why sample darkened at ph7 which I lowered using ascorbic acid ( only thing laying around the other day ) 

So main question ,  would citric acid   be more effective ( require less product) ? ( will be trying anyway just wanted some input regarding carbomer and ETA)


  • answered my own question  actually need to add sodium benzoate if im at 6-6.5  ( any lower it carbomer thins ) and yes citric acid use was minimal 

  • Generally, EDTA and sodium benzoate are not used for pH adjustment. Citric acid or lactic acid is used to decrease the pH from alkaline to acidic and sod.hydroxide or TEA is used to increase the pH from acidic to alkaline.
  • Thanks for the follow-up
  • For carbomer, I used  trolamine to bring up the pH to form a gel. I also used NaOH to bring up the pH to form a gel.
  • yes Use  NaOH  /TEA to increase the pH And citric acid to decrease the pH.
  • Why not just optimize the alkali rather than adding back the acid????
  • @chemist77 It's called the "back acid" technique, a peculiarity with Aqua SF1. If that's what he's using.
    Design of anti-aging creams, gels, and serums; shampoos; and therapeutic cosmetics. In-house label and box design capability.
  • Oops I never saw Aqua SF 1 mentioned in the thread, I am using Aqua SF1 myself and the next grade as well. 
  • You may try Lactic Acid Instead of Citric Acid.  It may require you to add a lot more Lactic Acid than what you should add from Citric acid.  If you use Citric Acid in the adjustment, it may decrease viscosity significantly either shortly after the adjustment or on the long run.  When you adjust with citric Acid, you may get pH in the spec range, but, by the time you test for finished product to release the batch, you may get viscosity on the minimum of the Spec. Range which could be released, but, by the time, the product stays on the shelf in the Retail Store and Customers buy it, it may become very watery.
  • If you like to try Lactic Acid instead of Citric Acid, You may try the adjustment in a Lab Batch with no more than 20% solution concentration of Lactic Acid till you reach the required pH range only : 6.0 - 6.5 because Lactic Acid has exfoliating property and result in skin peel.  You shouldn't increase the concentration of Lactic Acid in a batch more than 10% of the 20% Lactic Acid Solution.
  • I passed by a formula utilizing Carbopol with Lactic Acid in Skin Brightening Gel in case you like to look at it.[AP]

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