Emulsifier quantities

Formulating

Emulsifier quantities

Posted by em88 on January 5, 2023 at 12:57 pm

Hello,

I saw this formulation in a book and wondered about the emulsifier quantities.

2.00 Ketoconazole micronized

20.00 Propylene glycol

8.00 Stearyl alcohol

2.00 Cetyl alcohol

2.00 Span 60

1.50 Tween 60

1.00 Isopropyl myristate

0.20 Sodium sulfite anhydrous

0.10 Tween 80

q.s. 100 Water purified

Does anyone know why the quantity of Span 60 is higher than Tween 60?

Thank you

Pharma replied 1 year, 11 months ago 3 Members · 3 Replies
3 Replies

chemicalmatt

Member
January 5, 2023 at 7:35 pm

Affirmative. This combo of Sorbitan Stearate/Polysorbate 60 was taken directly from the original HLB Handbook authored by Bill Griffith for Atlas Chemical Company in 1957. Still works today! I know this annoys one of our esteemed colleagues here, who has been adamant about dissing the HLB system all along (and you know who you are.) The sulfite is in there as an antioxidant for ketoconazole stability. The TWEEN 80 seems totally unnecessary to me.
em88

Member
January 6, 2023 at 8:55 am

Shouldn’t the quantity of Polysorbate 60 be higher than the quantity of Sorbitan Stearate?
You are right about the antioxidant.
My guess for polysorbate 80 is that it is added as a wetting agent for ketoconazole when it is dispersed in water. After that, the suspension is added to the base cream.
Pharma

Member
January 9, 2023 at 5:42 pm

chemicalmatt said:

…I know this annoys one of our esteemed colleagues here, who has been adamant about dissing the HLB system all along (and you know who you are.)…

Not in all cases but most. It can work in simple systems… this one does look simple. However, it’s actually not even a classical HLB emulsion but a lamellar structured emulsion (10% fatty alcohols) and hence, the original HLB system doesn’t apply (not saying it can’t be stable, I’m saying that HLB math doesn’t matter). Sorbitan esters also form lamellar structures and the roughly 12% ‘high HLB’ emulsifiers are in the recommended range for proper hydration of the ‘low HLB’ emulsifiers (Span plus fatty alcohols). As a result, the proportion Tween to Span might have been copied from Griffin (with an -N, not a -TH 😉 ), might be LGN formulation, or just a coincidence or found by trial and error.

In addition to that, the 20% PG result in a higher apparent HLB as would be found using standard HLB calculations.

And that’s one example more in my collection of ‘Why not to use HLB calculations in cosmetics’.

Sorry @chemicalmatt, I simply couldn’t help it :blush: .

chemicalmatt

em88

Pharma