Viscosity problem

Larissa9Larissa9 Member
edited September 2020 in Formulating
Hello everybody,
I am on my final year of Pharmacy college (read: no experience) and working on a gel with glycolic acid and suspended olive pit particles that are suposed to work as mechanical body peeling. When I make this gel everything looks great for maybe two weeks then olive pits start to sediment. I chose a pH of 3 and currently considering to make it 3,5.
This is what I have now;

Aqua purificata 79,56%
Glycolic acid (70%) 5,72%
NaOH 0,42%
Hypromellose 2%
Xanthan gum 1%
Olive pit particels (500, Fagron) 1,2%
Cocamidopropyl betaine 9%
Vitis viniferae 0,4%
Aurantii aeth 0,7% 

How do you think I can stop sedimentation?
Thank you very much for your help.


  • PharmaPharma Member, Pharmacist
    If sedimentation is caused by a progressive viscosity loss, raising pH might be the solution. pH 3 is the lower end of stability for both polymers and I'd guess it's hydrolysis of these which would be responsible for said viscosity loss.
  • Thank you for your suggestion, makes sense.
    I will try with pH 3,6 which is also the pKa of glycolic acid and see what happens.
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