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Question

Posted on: March 6 2013

Problem with precipitation of Tretinoin Hydroquina 4% tretinoine 0.03% Vitamin C 0.2% propylene glycol 10% ethanol AQUA DIST AA 100ML

I tried the following:
  • the Vit C mixed with propylene glycol and then dissolved in the water (phase 1)
  • the Tretinoine and Hydroquina dissolved in the ethanol under heating. Afterwards let Cool (phase 2)
  • when merging Phase 1 and 2 a precipitation occurs
how do I prevent the onset of this precipitation?

Answer

The prescribed method is already mentioned several times between the solved questions.
  1. Prepare your alcohol phase and apply those in a measuring cylinder and add 10ml propylene glycol;
  2. dilute with water under constant stirring and under observation of formation of a precipitation.
  3. forms a precipitate add 10 ml of extra ethanol; mix and see if precipitation dissolves; if not add 10ml ethanol yet.
  4. dilute further with water as described under 3 to 100ml is reached. Note the total amount of additional ethanol added.
  5. dissolve on 0.2% vitamin C
Correct the composition in your registry.