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Need help with hydroquinone formula
I made made this same base with 2% hydroquinone and everything is fine. I have Doctors who want 4% and more. As soon as I add 4% hydroquinone to the emulsion at 120F it all separates. Also tried premixing in water and then adding that. Any ideas? Thank you
Water 71.6 %
Prop Glycol 2.28 %
PEG-40 Stearate 2.0 %
Cetyl Alc. 2.0
GMS 165 3.0
IPP 2.0
Soybean Oil 4.0
Mineral Oil 2.0
Hydroquinone 4.0
Water 3.0
Sodium Metabisulfite 0.5
Cetearyl Alcohol 2.0
Dimethicone 1.0 -
15 Replies
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The only emulsifier I see is PEG-40 Stearate (Myrj S40). Have you considered a co-emulsifier? Maybe one of the Span’s (Polysorbates)?
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Bob, GMS 165 is in there too. Also some Cetearyl alcohol
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Actually, Bob, it appears Dave’s got Arlacel 165 in there too - the old PEG ester workhorse. That being said, you may want to convert this to an ether alcohol system and get away from the esters altogether. The Steareth-2/Steareeth-21 combo usually works. ( I just use Steaereth-12 and split the proverbial HLB difference.) Hydroquinone is far more electoryltic than folks remember, and that metabisulfite is a contributor too.
I’ll pose another issue for you here, or open another thread: have you tried assaying this on HPLC with a UV detector yet? I recall having to resolve the two enatiomeric forms of hydroquinone by varying the mobile phase polarity program. It was a bitch! Wish I still had that test method, I’d email it to you.
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I don’t really consider Cetearyl Alcohol to be an emulsifier. I did think, however that GMS 165 was just a peculiar way to identify Glyceryl Mono-Stearate, so I missed that piece, sorry.
That being said, I think Matt’s got the right idea: Steareth-2/Steareth-21 combo, with the possible addition of polysorbate 60 and/or what used to be called Arlacel P-135 ( now Cithrol™ DPHS from Croda = PEG 30 Dipolyhydroxystearate)With the use of the Steareth-2/Steareth-21 combo, the Cetearyl Alcohol does act as an emulsion stabilizer/LC booster. I’m not at all sure it behaves the same way with PEG-40 stearate. -
It’s strange, at 2% beautful white lotion that I have sitting in a jar since 7/2013 still white.
At 4% as soon as you add the hydroquinone it separates. Here is list of ingredients in other 4% product:
Tri-Luma
Inactive:
butylated hydroxytoluene, cetyl alcohol, citric acid, glycerin, glyceryl
stearate, magnesium aluminum silicate, methyl gluceth-10, methylparaben, PEG-100
stearate, propylparaben, purified water, sodium metabisulfite, stearic acid,
and stearyl alcohol.This really has me stumped. I can’t even get 4% and the customer wants a 5%, 10% & 15%
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magnesium aluminum silicate is the key.
Use the Veegum HS grade for maximum electrolyte stability and minimum acid demand. -
Need to know what you people think. Made the formula below. Everything looked fine. Lotion was nice and white. Adjusted with citric acid solution to pH 2.5. The product took on a slight yellow tint, not a big problem. It developed a real weird smell, almost metallic like. You could also actually feel this in your throat when smelled. Any ideas what it may be or how to prevent?
Water 43.73 %
Prop Glycol 17.5 %
PEG-40 Stearate 2.0 %
Cetyl Alc. 2.0
GMS 165 5.0
IPP 2.0
Soybean Oil 4.0
Mineral Oil 2.0
Hydroquinone 5.0
Water 3.0
Sodium Metabisulfite 0.5
Cetearyl Alcohol 2.0
Dimethicone 1.0 -
I suspect your sodium metabisulphite is the culprit
in acidic media it degrades into sulphur dioxide, which has a harsh, acrid smell and is very nasty stuff altogether
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Yes, that was the other smell. Kind of sulfur like. However, sodium metabisulfite is used in most hydroquinone creams to prevent oxidation as well as a low pH for the same purpose.. The same basic formulation using 2% HQ at the same pH does not have that smell. Thank you for your input.
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was there any difference in the amount of acid you needed to adjust the pH in the 2% and 5% hydroquinone formulas? (I ask as the actual quantity of acid is sometimes a more significant factor than the pH itself)
in my view, the only other thing in that formula which has any potential to generate a volatile substance almost instantly is hydroquinone itself - if it were oxidised
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Our lab actually does not usually measure the amount of citric acid solution needed for pH adjustments. They usually just adjust to the required range. This project has been a pain in my side. 2% is no problem but this doctor wants a 5%, 10% and either 15% or 20%.
I appreciate your thoughts on trying to help.
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Anyone have any idea why many HQ formulas have a large percentage of Stearic acid in them? I am talking about 12% to 18%??
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@Bill_Toge This morning we premixed Na Metabisulfite in water (as we do in our process) and smelled it. It has that sulfur/metallic smell just being mixed in water with nothing else added. The pH drop later on may bring it out more.
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my two pence worth:
1. if possible, switch from sodium metabisulphite (Na2S2O7) to sodium sulphite (Na2SO3) - it’s chemically more robust, and the lower molecular weight means you’ll need less of it to achieve the same effect; having made up an 0.5% solution of sodium sulphite in the lab and acidified it, I found that no odours were evident until I’d added several percent of citric acid and the pH was well below 4
for what it’s worth, the company I work for has a history of successfully manufacturing oxidative hair dyes containing bases chemically similar to hydroquinone, in alkaline formulas (much more likely to promote auto-oxidation than acidic formulas) and we’ve found 0.2% sodium sulphite works well, provided the product is given the absolute minimum exposure to air (this usually involves covering the surface of the bulk liquid with a plastic sheet)
2. set the pH of your formula as high as you can get away with, so you don’t have to use as much acid in the formula, and reduce the risk of degrading your antioxidant
3. put a chelator in the formula - metal ions, particularly iron and copper, are terrible for inducing auto-oxidation in oxidative dyes, and from what I understand the same is true of hydroquinone
hope this helps!
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Bill,
The thing is the final pH needs to be around 3.0 so based on what you tell me regardless of which I use based on the low pH we will still get that smell.
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