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Glyceryl stearate citrate emulsifier and pH range.
I have been having some minor issues with a cream that is Montanov 202 based (INCI: Arachidyl Alcohol (and) Behenyl Alcohol (and) Arachidyl Glucoside) and supported by Glyceryl stearate citrate.
As I was reviewing the re-packers description for GSC it says:
Stable emulsions from pH 5.5 - 8.0.
If that is accurate…that is a pretty small window to formulate in!?When I go on ULP….the Mfg says this:
(GSC is) Well suited for making emulsions with a
slightly acidic pH-value (corresponding to
the natural pH-value of human skin)I had been targeting a 5.0 pH. Is this out of the suitable range of GSC?
Funny thing is….Evonik has some combo emulsifiers (with GSC) that have this tag:
It is suitable for the formulation of O/W creams
and lotions with all types of cosmetic oils at a
pH of 3.5 to 8.5.So does the pH range of GSC…depend on what it is partnered with? Independently, the window is small…but at a co-emulsifier….the window can be opened a great deal? Mont 202 says it can go down to 3.0 pH.
Guess what I am ultimately asking is…. Is a pH of 5.0 acceptable for an emulsion using M 202 and supported by GSC? (Just for the record…a little Aristoflex and Carbomer in there as well.)
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1 Reply
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Depends… see, GSC becomes slightly anionic at pH above a certain value (I don’t know the exact numbers to calculate it) which imparts improved stability in droplet-based (aka standard or traditional) emulsions. If used as co-emulsifier in lamellar networks, it’s pH independent (too low will kill the emulsion anyway and too high will lead to hydrolysis of GSC but also 202).In your case I’d say that you rely somewhat on the anionic nature; given that GSC doesn’t have an on-off switch but gradually becomes neutral at lower pH, it seems unlikely that dropping pH by 0.5 will neutralise the whole effect (as an educated guess, your worst case scenario would be that you have to add a bit more GSC to compensate electrostatic losses).
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