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pH drift in Self Tan Formulas
HI Everyone,
I know that self-tan formulas containing Dihydroxyacetone (DHA) show pH drift over time. But what I noticed is the drift depends upon the type of dosage form. I formulated a lotion, gel, and mousse. All of them had a final pH of 4.25. The pH of lotion and mousse was 4.17 even after a month but pH of gel reduced to 3.95 over night and stabilized around 3.65, which is very low. My worry is drifting of pH lower than 3.50 over time.What recommendations do you guys have to help self-tan formulas not to drift pH? Also what is a odor blocking technology? Is it just adding more or strong fragrance to the product? -
1 Reply
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Cosmo, if memory serves, DHA undergoes slow acid-catalyzed hydrolysis to glycolic acid, whereupon you get the extra protons that lower pH. The more water you have in your formula, the likelier this will happen. Perhaps cut it with some propylene glycol. I’m unsure whether a buffer would help, but you may try a glycolic/glycolate buffer system at pH 4.2 and check it out.
There have been many odor blockers over the years, the most common being the lactones. These work in water-based systems. ICI (oops, I mean Croda) might still offer Forestall, which is an alkyl quat that used to work well masking thiogylcolate odors in permanent waves. Other than that, your first guess is probably true: more fragrance, more better.
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