Triacetin Alternative for After Sun Lotion

PharmaPharma Member, Pharmacist
edited July 2020 in Formulating
This urea after sun lotion calls for triacetin... I don't have that in hand and am wondering with what I could replace it (triethyl citrate, pentanediol, DMSO, or maybe an alcohol?) or if it doesn't serve any real purpose and can be omitted without any stability issues.
Thanks for your inspiring thoughts on this!


  • EVchemEVchem Member
    I see it being used as a humectant  in BASF material 

    AMC Advanced Moisture Complex NP

     with trehalose,  sodium PCA, hexylene glycol, polyquat 51... so maybe any of those would be a safe substitute
  • lewhitaklewhitak Member
    edited July 2020
    Hello Pharma!
    I recently worked on a 25% urea w/w solution and found the only addition that stabilized my pH was triacetin. You could try the triethyl citrate and see if maybe it will modulate the pH in the same way? 

    I checked the AMC Advanced Moisture Complex NP and even it has triacetin in it:

    Glycerin (and) Aqua (and) Sodium PCA (and) Urea (and) Trehalose (and) Hexylene Glycol (and) Polyquaternium-51 (and) Triacetin (and) Caprylyl Glycol (and) Sodium Hyaluronate 

  • PharmaPharma Member, Pharmacist
    Ah, stabilisation of urea. That might be the reason Evonik seems to use it only in their high % urea base formulations.
    A quick search revealed that high % urea tends to recrystallise resulting in a sandpaper feeling and triacetin (buffering through hydrolysis), lactic acid (low pH), or adsorption to polysaccharides help preventing that. Triethyl citrate might actually work as well...
    Thanks so much for your inputs, that's exactly what I needed!
  • Yes! I wish I could remember who in the forum mentioned it, but there was a company who would spray urea solution on starch and then use that in their creams to avoid urea crystallization. 
  • PharmaPharma Member, Pharmacist
    I think that was even me (how embarrassing). :blush:
    Triacetin simply didn't ring any bells. Must be the first sign that my brain's getting old... but once it was re-attuned to urea stability/degradation rather than everything else, memory came back, at last.
    Now I'm having a hard time deciding whether to risk using solely triethyl citrate or including a buffer. Lactic acid/lactate would fit in nicely but it's buffering range is off...
  • @Pharma haha! Your database is just getting filled to the brim with ingredient facts is all! 

    Personally, the inclusion of a lactic acid/sodium lactate system didn't give greater stability to the product versus just including the triacetin. There was less drift technically since the starting pH was higher with the buffer system included, but overall I wouldn't say it did much better. 

    I didn't try it with the ammonia salt of lactic acid, though. Maybe that would help more??
  • PharmaPharma Member, Pharmacist
    I'm now playing around with triethyl citrate plus a lactic acid - histidine buffer at pH 6-6.1.
    From the info I could gather, quite a lot of buffer may be required (that base formulation is with 20% urea) and histidine ain't the cheapest...
    In theory, I should take a strong mineral acid instead of lactic acid but lactate has its perks in skincare.
    Finding a weak base as alternative for sodium hydroxide isn't that easy (okay, it is, but I don't like these ingredients in my cosmetics) and it seems more reasonable than the 'traditional' lactic acid - sodium lactate buffer which will be beyond it's buffering range and that on the wrong side too. Sure, a weak-weak buffer such as mine ain't what would commonly recommended... We'll see if it still works.
  • Agreed on the lactic buffer. I wanted to try it out based on the results of this paper, but ultimately found the triacetin to be more useful for stabilizing the pH after an initial spike. 
    This pH spike occurred at RT within two to three days after mixing.

    I am very curious how your lactic acid - histidine buffer will go! Personally, I will pay more money for histidine to get a safer and effective buffer system :)  
  • PharmaPharma Member, Pharmacist
    I'll keep you in the loop ;) .
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