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When is pH not relevant
Hi All
Just looking for some general guidelines for when pH Is not relevant
Ie how much water is needed in a formula to get a accurate pH?I am making a face cleanser with a high concentration of oils and surfactants it leaves 45% water.
Is there a need to measure and adjust pH?Same for w/o emulsions is pH relevant?
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4 Replies
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PH is relevant in all cases where water is present even at 1-5% wt/wt
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because pH meters are electrochemical devices, the relevance and reproducibility of any readings depends on the conductivity of the product, which in turn depends on its composition
as the conductivity decreases (whether this is due to a lack of ionic salts, or the presence of non-conductive co-solvents), the measured pH readings will become less accurate, less consistent and less meaningful overall
in anhydrous products and W/O emulsions, the continuous phase generally has little to no electrical conductivity, so any readings are essentially meaningless
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Good quality pH meters will adjust and account for the lower water content and conductivity (as well as temperature). Of course, if you don’t have one to this standard, it is much less accurate.
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Hi,
Ok thanks Bill_Toge yes thats what I was taught so in general manufacturers I know dont even bother reading the pH of w/o or adjusting pH….
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