[jeremien]

You can test pH of  your
product at different dilution (with deionized water) … you will certainly observe a flat curve up to 1/10
dilution. Higher dilution should affect the pH

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The question is if your mixture of ceramide/cholesterol/fatty acid is able to penetrate into the SC. You may need a vehicle.

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pharmaceutical or medical device

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You can ask to Santa Claus the Ika Tube, there is turrax unit tubes available … 500$ the basic version 

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Imutec SP1 from Beneo is a polymeric surfactant derivated from Inulin. It provides very good steric repulsion in dispersions.

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Is the combination Potassium Sorbate / Vit. C a real issue? I know that it was already comment on this forum for the residual Benzene produced that is induced by light. I understand that potassium sorbate in formulation is used at acidic pH <5 and is mainly on the form of sorbic acid., thus at the concentration of use of both products it will no be an issue.   

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I was just looking to the technical documents, and only very general considerations on the solubility of ascorbyl palmitate in oil  

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@cossci21, at which concentration is ascorbyl palmitate soluble in sunflower oil?

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the french brand Gallinée sell cosmetic containing probiotic, prebiotic and lactic acid. I understand that they preserve their products thanks to relatively low pH (4.5), and high active ingredient amount (such as lactic acid) … and cream are produced under GMP

[jeremien]

no oxidation test?

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it has a structure very close to ascorbyl palmitate. What about its stability?

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3-0-ethyl ascorbic acid is water soluble isnt it?

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Thanks for this very interesting elements on the niacinamide hydrolisis. 
What are your favourite anti-inflammatory/soothing actives apart from the niacinamide? Personally I like the effect of alpha-bisabolol.

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Is sensiva PA 40 acting as a preservative or as a preservative booster?

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It’s always the same problem, you can conduct study,
but rarely, all data are positives, so “ALL” the companies just do
not present the bad results that go against the claims they look for. If
pharmaceutical company are doing the same with clinical trial how do you think
that cosmetic one are not using only the good results.

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here you have the pdf

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try this link if it works for you: http//sci-hub.io/10.1002/0471440264.pst610

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DSM (https://www.dsm.com/corporate/home.html) and Merck Ronacare (http://www.merck-performance-materials.com/en/cosmetics/ronacare/ronacare.html) also propose Niacinamide

[jeremien]

So if i understand your point, better add the EDTA at the end, when the system can avoid formation of crystals

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i ask because i have tried it , and i notice some
small crystals. Since i see that many formulation have edta at 0.1%, i’m asking
to know if it’s normal to have the final formulation with some unsolubilized
edta. 

[jeremien]

@Bill_Toge  I agree, that in the industrial report, this in not
consistent with a phase inversion, but look like a uncompleted emulsification
process.  If the system contain only a high HLB surfactants you
will never form a W/O emulsion. To invert the system by PIC you need
equilibrate HLB surfactant system (low and high HLB in the mixture to get an
average between 8 and 12) to form lamellar liquid crystal or bicontinuous
microemulsion in the dilution pathway. 

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@Bill_Toge , not agree with Canard
1: Phase inversion can occur not only with tºc (with ethoxylated
surfactants), but also by change in the composition by the so-called phase
inversion composition (PIC) technique. It takes advantage of the change in
surfactant curvature along dilution pathway. To be able to carry out a phase
inversion by composition you must be aware of the phase behavior of your system
(ternary phase diagram) You can find a lot of literature of this method
(profesor Solans, Kunieda and Salager are reference in this field). Furthermore
it is a very useful method since you can produce small and homogeneous droplet
size without adding high energy to the system.

[jeremien]

do you have a pH meter? Normally it indicates the
conductivity. 

[jeremien]

Can you measure conductivity? It’s the best measurement to determine if you have O/W or W/O emulsion. For W/O/W you need a microscope.

In your emulsion you have a low HLB emulsifier (polyglyceryl-3 diisostearate) and high HLB one (polysorbate 20), so you are likly to form a multiple emulsion or maybe you can have some lamellar phase since you are at a global HLB of your system close to 10.  At this HLB you can have some surprise with temperature. 

[jeremien]

Thanks to all of you for your comments. @Bobzchemist when you say: Pemulen is synergistic with Carbopol,
you mean in term of viscosity? I will try it.

@ David  i use olivem 1000 because i like the
sensorial feeling it gives to the formula. And I would like to jump to tottaly
ecocert formula. By the way, is there any ecocert thickener polymers?