Saturday, June 19, 2010

Question: Differences between cetrimonium bromide and cetrimonium chloride?

Kontakt asked this question: As I understand it, the only difference between centrimonium bromide and cetrimonium chloride is the negatively charged ion: chloride or bromide. What differs between these two compounds in effects, and why? In solutions, the ions should be free from each other so unless the chloride/bromide ion does something in itself, I fail to see what the difference should be. Similar things are true for many pairs of related compounds, SLS/ALS for instance. Sodium or ammonium. As long as you adjust pH, is there really any major difference?

Cetrimonium bromide is actually cetyltrimethylammonium bromide. Cetrimonium chloride is hexadecyltrimethylammonium chloride, so there are differences other than the negatively charged ion.

Having said this, when you are buying bath and body supplies, you aren't getting the pure version of a product. When I buy cetrimonium bromide, I'm buying 27% to 29% cetrimonium bromide with cetearyl alcohol making up the rest, and it comes in a waxy flake format. When I buy cetrimonium chloride, I'm buying a liquid with about 25% active ingredients with preservatives and water making up the rest.

It's hard to compare different surfactants between companies because each brand is different depending upon how much of the active surfactant is in the solution, other ingredients added by the manufacturer (preservatives, conditioning agents, thickeners, and so on). For instance, I generally use SLeS in my body washes, but thought I'd try ALeS because my SLeS bottle was almost empty. The ALeS thickened the mixture up so much, I turned it into Jell-O with 1% Crothix - I'd normally need 2% for SLeS to thicken it nicely. This has more to do with the extras in the SLeS vs. ALeS mixture than the surfactants themselves, but it's still very relevant when you're making a product. And then we have to consider the moles of ethoxylated molecules...

Buying cosmetic supplies is like buying salt - we aren't buying straight NaCl. Just as table salt contains iodine, dessiccants, stuff to help it pour out, we find the same thing with our supplies. You aren't buying straight SLS or concentrated cetrimonium chloride. You're buying something containing water, preservatives, thickeners, conditioners, and so on. And each manufacturer will add or remove something that will make their product different from their competitors. And then there's differences in moles of ethoxylation and titer points and all those other lovely things that make cosmetic chemistry so interesting!


kontakt said...

I completely missed this post! but I wondered why my comment didn't show up where I put it :P and was thinking of re-posting it.

In your two pictures, the cations (positively charged ions) actually ARE identical. They are just using different system for depicting organic substances. Counting... 16 carbons in the chain, 19 altogether. Yupps. "Cetyl" is a trivial name for hexadecyl (which means 16), I guess.

The rest of your post totally makes sense, though. I have been a bit frustrated at how mixtures of substances are called by a name that makes you think they consist of only one kind of molecule. This is my behentrimonium chloride: solid, pellets. Worth to keep in mind when I read yours, and other Northern America-based people's recipies. The trade names used here differ, and sometimes also the actual mixes of substances.

kontakt said...

(and I do wonder if this cetrimonium chloride from this firm does contain any cetyl alcohol or not... unfortunately I don't speak German, and have problems communicating with the owners)

Susan Barclay-Nichols said...

Interestingly enough, it says "Incroquat" at the end of the information, so I'm wondering if this is BTMS-25 or BTMS-50 (it can't be Incroquat CR). They call it TMC, which generally means it's BTMS-25, although this could be a language thing.

They recommend using 1/3 this product, 2/3 cetyl alcohol at 1% to 2%, but I can't figure out whether this is for emulsifying or for a conditioner. This isn't cetrimonium chloride - this is behentrimonium chloride, which is a different creature altogether - the equivalent of BTMS, not cetac. I haven't seen a waxy product that didn't contain a fatty alcohol or fatty acid, so it's safe to say that it probably contains one or the other. Most of the time they contain a humectant as well like propylene or butylene glycol. Cetrimonium chloride is generally found as a liquid without fatty acids or alcohols.

There are differences in cetab and cetac - for instance, cetab can penetrate the hair cortex (p. 692, Handbook of Cosmetic Science & Technology, 3rd edition; p. 416, 2nd edition.) "The interaction between cationic conditioners and the hair fiber mainly occurs at the surface; however, low-molecular weight materials may penetrate the interior by intercellular diffusion. Cetrimonium bromide (CETAB), e.g., can penetrate the cuticular sheath as well as cortex." Cetac is not capable of doing this.

As for the differences in what we're using, this is why I try to include the INCI for various products because different companies call similar products by different names. We can find Incroquat TMS-50 listed as conditioning emulsifier, company name's conditioner emulsifer, Incroquat emulsifier conditioner, BTMS, and so on, so it's valuable to know what makes up the products we're using so we're not tied to one supplier. If the supplier doesn't offer an INCI...well, that's just frustrating!

kontakt said...

Oops, behentrimonium. Yupps! My mistake. I blame it on being tired yesterday night. "This is the replacement for Incroquat", they had Incroquat before but now this version that allegdedly contains to cetyl alcohol.(And similar reasoning goes here of course, differences to BTMS - methyl sulfate ion vs chloride. Big difference or not? My guess is not,except that you'd add mor cetyl alcohol, but I wouldn't bet on it.)

Susan Barclay-Nichols said...

If you take a look at the INCI for BTMS-50 and BTMS-25, you'll see there are differences in the fatty alcohol and the BTMS-50 contains a humectant. Incroquat could mean one of many products - there's Incroquat CR, OSC, 18-MEA, BTMS-50, to name a few. (Incroquat is a product line from Croda that generally includes conditioning agents.)

I can't find any information comparing the methosulfate with chloride, except the odd anecdotal comment that the chloride is "cheaper" and a comment from the Incroquat BTMS-50 brochure that states the methosulfate may be non-irritating due to a lower critical micelle concentration unique to it (page 3, bottom).

A Fajardo said...

Hi Susan, I was wanting to make your conditioner recipe (Basic Rinse off conditioner for dry, damaged hair) and ordered my ingredients. I just noticed that instead of ordering cetrimonium bromide, I ordered cetrimoniim chloride by mistake. I just wonder if I can still use cetrimonium chloride for your recipe:

Basic Rinse off conditioner (dry, damaged hair)
7% BTMS-50 or cetrimonium bromide
3.5% cetyl alcohol
.5% or 1% preservative
1% fragrance
88% water

Also, the supplier was out of stock of BTMS-50, so I ordered BTMS-25. I plan to experiment and know the difference of using BTMS and cetrimonium chloride.
Thank you!

Susan Barclay-Nichols said...

Hi A! I have loads of recipes using BTMS-50 and cetrimonium chloride on the blog. The latter is one of my favourite ingredients!

Endtime Warriors said...

Can you provide your supplier information? Thank you

wbliss said...

Actually the Cetrimonium part is exactly the same for both Cetrimonium Bromide and Cetrimonium chloride. They are both hexadecyltrimethylammonium or even cetyltrimethylammonium. Unfortunately with organic chemistry you are given lots of options for naming chemicals. The only difference is a Bromide ion with 1 negative charge or a Chloride ion with one negative charge. The Bromide ion has twice the molecular weight, is a bigger atom so the weight is more and the charge density is less. So there is likely to be some very small but most likely negligible for our purposes difference in effect. Unfortunately I cannot find any scientific discussion online that would help me decipher if they (bromide VS chloride) perform equivalently in Personal Cosmetics. Me? I am a personal cosmetic chemist and laboratory manager at a manufacturing and packaging company. If you visit hotels and have used their amenities it is extremely likely you used our stuff.

wbliss said...

I will say this. The positively charged part is what will stick to your negatively charged hair and perform the conditioning effect without leaving a greasy feeling. The negatively charged ions (bromide or chloride) get washed away and have no effect. So in the end I think you have your answer there.