PH Drift - Is both an UP and DOWN ingredient needed ?

mikebavingtonmikebavington Member
edited February 2014 in Formulating
I was looking at KY Jelly and its ingredients:

Water - Solvent, Dilutent, Moisturizer
Glycerin - Humectant
Hydroxyethylcellulose - Emulsifier, Thickening, Stability 
Chorhexadine Gluconate - Preservative
Gluconolactone - Chelating agent, PH drop, PHA, Moisturizer
Methylparaben - Preservative
Sodium Hydroxide - PH increase

So, I think I understand the purpose of all the ingredients, however, I just wanted to point out the Sodium Hydroxide at the end of the ingredient list and ask if both a PH up and PH down ingredient is necessary in each formula to prevent PH DRIFT. Can you simply put one PH ingredient in a formula, reach the desired PH and be confident that it wont drift that much (depending on the ingredients), or has the industry found out that two PH ingredients - up and down -  are needed to prevent the drift. Any hard and fast rules?

Comments

  • By the way, I realize that all ingredients, effectively, contribute to final PH; but in general, most formulas seem to have distinct PH influencing ingredients.
  • chemicalmattchemicalmatt Member, Professional Chemist

    Mike,

    I think the only rule is how exacting your ingrdient disclosure needs to be to satisfy the legal department in a case such as this.  Were this a routine personal care formulation, I would not bother reporting the NaOH, and none would be the wiser, especially since you and I know it does not exist in its purely ionic form but more so as a salt with methylparaben in this case.  After considering any possible legal claims against the KY makers (J&J, right?) by KY users could prop up, I'm sure the lawyers said "list it".

  • Bill_TogeBill_Toge Member, Professional Chemist
    at my last workplace, we made some products where the pH varied a lot from batch to batch - if a given batch was outside the pH spec, caustic soda and citric acid were respectively used to bring the pH up or down

    in process, the pH of the batch started high and was brought down with citric acid, so caustic soda additions were very rarely needed

    however, it was still included on the ingredients list, because it was intentionally added to the product at the design stage, even though most batches didn't contain it in practise

    I suspect it's being used in the same way here - to raise the pH if it's initially too low
    UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
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