Azeco Cosmeceuticals

Question: Pricing is fine….I make a lot of margin on these products. This is a mens hair care product but I’m looking to use fairly diversly. I’m pretty happy with the Azalaic acid. To be ho- nest its better than those bogus herbal additives that do nothing but boost INCI. I’ve been formulating with ozone grade but I’ll order a kg in the next couple of weeks. I see you guys micronize it. I have questions on the activity in the free acid or neutralized state. I’ve been pretty careful not to neutralize by post adding it to a PH of 5.5. But not sure if the is any difference in the free or salt state. Answer: Azelaic acid is a dicarboxylic acid and has therefore two dissociation constants. pKA1 = 4,55 & pKA2 = 5,50. As a consequence of being a weak dicarboxylic acid the ratio azelaic acid/monosodium azelate/disodium azelate is pH dependant. To give an example of the calculation for pH=5,0 ([H3O+]= 1x10-5).

Two equilibrium equations:

H2A + H2O ç è HA- + H3O+ HA- + H2O çè A2- + H3O+

With the two dissociation constants.

KA1=[H3O+]x[HA-]/[H2A] = 2,82x10-5 KA2=[H3O+]x[A2-]/[HA-] = 3,16x10-6

Furthermore the mass balance reads: [H2A] + [HA-] + [A2-] = C After substitution of [H3O+]= 1x10-5): we are left with three equations with three unknowns, and that gives only one solution. Calcu- lus gives: [H2A] = 0,213xC

[HA-] = 0,598xC [A2-] = 0,189xC

In other words: at pH=5,00 21,3% of the amount of azelaic acid present as the free dicarboxylic acid, 59,8% is present as the monoso- dium salt and 18,9% is present as the disodium salt. When another pH value would have been chosen another concentration profile is applicable. I do not have a picture for azelaic acid, but I have a picture for another dicarboxylic acid: fumaric acid.

Mussenberg 1 • 6049 GZ Roermond • The Netherlands

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