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Emulsion resistance to altering pH with lactic acid
Hi all. I made a 100g sample o/w emulsion following a formula I have been making for quite some time, but changed up the actives, namely adding 1% DMAE Bitartrate. Typically with the original formula of a sample this size, it comes out at about pH 7.5 and requires about 5-8 drops of 90% lactic acid solution to bring it down to 5.2-5.3. This new formula came out at pH 7.5 as well, but took several milliliters (yes!) of 90% lactic acid to bring the pH to 5.6. It was suggested to me that perhaps the free (not neutralized) dmae was reacting with the lactic acid, and was unable to bring the pH of the formula down until it was neutralized. Does this sound accurate? Is there a more efficient way to utilize DMAE Bitartrate without encountering difficulty adjusting pH? Thank you for any thoughts!
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2 Replies
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Well, DMAE bitartrate does buffer but 0.5 ml 90% lactic acid will fully react (hypothetically) to DMAE lactate and tartaric acid. The resulting pH will be very low.You’ve got a different problem, maybe mislabelled lactic acid or a broken pH meter? -
I calibrated my pH meter and tested it against strips, just to verify, and the readings were consistent. I also switched sources of lactic acid after failed adustments thinking perhaps the current batch was no good (although I had just used it last week with no issues), and there was no difference. I will check the pH today (24 hours after creation) and note any changes. Thank you - I will post the full formula as well to see what might be the other issues.
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