Sunday, October 18, 2009

EDTA - a chelating and sequestering anti-oxidant

EDTA (or ethylenediaminetetra acetic acid) is a wonderful polyamino carboxylic acid that has the ability to chelate, sequester, and offer anti-oxidizing properties to our lotions. And we only need to use 0.20% to get maximum benefits in our lotions and surfactant based products! (For a cool rotating EDTA molecule, click here!)

What exactly is a chelating or sequestering ingredient? EDTA binds with metal ions (mostly calcium and iron ions) and keeps them from being reactive with our various ingredients. These metal ions can precipitate in our creations, forming a metallic solid that is really unpleasant. And the metal ions can keep our surfactant mixes from foaming as well as they should, and can remove the scum that builds up on the tub after a bath.

We know auto-oxidation with metals in the oils and water can promote rancidity, so adding EDTA to our creations will bind those metals to the EDTA and slow down the auto-oxidation process. (Which is also another reason to use purified or distilled water - get rid of those naughty metal ions!)

On top of all of this metal binding goodness, EDTA can behave as an auxiliary preservative to kill off those nasty microbes. There's always a chance a beastie will adapt to the preservative in our lotion and learn to live there - eek! - but the chelating agent disrupts the outer lipid layer of the microbes (where stability is calcium and magnesium ion dependent), which increases the penetration of the other anti-microbial preservatives into the bacterial cell!

EDTA is found in a salt form when we buy it from our suppliers - either calcium or sodium - to increase solubility in our creations. It is suggested you use tetrasodium EDTA for alkaline products (pH over 7) and disodium EDTA for products in the pH range of 3.0 to 9.0. We can use it in lotions and surfactant based creations at up to 0.20%, which is enough to do the job (but check your suppliers' recommendations). Add it to your water phase.

Join me tomorrow to see how we can add EDTA to a lotion formula for all that chelating goodness!

20 comments:

Aesthete said...

Really looking forward to your post tomorrow, Susan....I've learned so much from you, I can't thank you enough.

Aljonor said...

Hi Susan: I want to know if using EDTA means you don't have to add citric Acid in your products?

Thank you

Susan Barclay-Nichols said...

Yes, if you're using the citric acid as a chelating ingredient. If you're using it as a pH adjuster, then you still need to use it!

Anonymous said...

With regard to tetrasodium EDTA, I wanted to see its strucutre and found it. But I'm a bit puzzled why it is depicted with the Sodium ions kind of floating around the compound, rather than attached to it. Does this correspond to reality or is it just to emphasize what happens when you mix it with water (I suppose it then turns into EDTA, picking up H+ ions?)? Here's the link => http://www.chemspider.com/Chemical-Structure.5914.html. Thanks
Pete

Phebe said...

Hi Susan, thank you so much for all the information you share so freely on your blog. I can learn so much from you!
I have a question about EDTA: it is said that EDTA is very environmental unfriendly. Do you have any ideas or comments about that?

Thank you

Aishwarya Prasad said...

Hi Susan, i am manufacturer of Hair and Facial gel and use Carbomer 940. I use 0.05% Disodium EDTA in my formulation; but my gel is losing viscosity. Kindly guide me what can be the possible reasons

Susan Barclay-Nichols said...

Hi Aishwarya! If you are writing to me for help on a recipe, please include your recipe in percentages and creation process. If you don't share this information, I can't provide help. I don't have time to do the back-and-forth thing asking you for information I need to help you, so include everything and be as specific as necessary.

Jenifer said...

Hello, Susan! I promise I tried to find out as much as possible before bothering you with this question, but I can't find a satisfactory answer. In foaming bath butter, there is both Tetrasodium EDTA and phenoxyethanol...but that requires an additional preservative on top, correct? I've also recently seen small companies using that combination in their sugar scrubs (purely oil-based) as the sole preservative. EDTA can kill beasties, but does that make it a fungicide? Thank you so much! <3

Crystal said...

1st off I love your blog, now please correct me if I'm wrong. If I'm using Grapeseed oil as one of my ingredients in a product, does that mean I need to use the EDTA? Lets say I'm creating a lotion or a body butter using grape seed oil, does it have to include EDTA? If so what kind, from what I understand there are 2 types of EDTA. If I'm using citric acid as a chelating ingredient, do I still need to use the EDTA when using grapeseed oil? I love grapeseed oil, and I have a full 8lbs of it. I don't want my products to go bad before my customers have a chance at using it. Any help and or advice would be greatly appreciated. Thanks :)

Susan Barclay-Nichols said...

Hi Crystal. I think you're asking if you can use EDTA as an anti-oxidant with an oil? No, this is a water soluble ingredient that works as a chelating ingredient. It can behave as an anti-oxidant in the sense that the metals in your water won't cause auto-oxidation, as I mention in the post. If you use it in a water containing product like a lotion, it will work with the water part of the product, not the oil part. This will have no noticeable impact in retarding the rancidity of grapeseed oil.

What you want is an anti-oxidant like Vitamin E for grapeseed oil. I would caution you against using this in a commercial product, though. It has a three month shelf life. There are some great oils you can use in its place, like hazelnut or macadamia nut oil, that have seriously longer shelf lives. I never ever advise anyone to use grapeseed oil in a product you're selling. It goes rancid so quickly!

Have fun!

Amanda Dvorak said...

Wait NOW I'm confused. I know grape seed oil goes rancid quickly but this is what soap queen said about Hazelnut oil (only having a shelf life of 3 MONTHS!)
For example, let’s take a look at the Oat Oil Cleanser recipe for oily skin. You can see the recipe below. Each oil has a slightly different shelf life. Castor oil has a shelf life of approximately one year, hemp seed oil has a shelf life of approximately two years, sunflower oil has a shelf life of approximately 3-6 months, hazelnut oil has a shelf life of approximately 3 months. The shelf life of the product is 3 months due to the hazelnut oil. If the hazelnut oil is used past its shelf life, it may start to smell rancid, or change colors slightly within oil cleanser. This would make the entire product rancid. This oil cleanser does contain vitamin E oil which is thought to extend the shelf life of oils. But, it’s impossible to say exactly how much longer it will make the oils last.

I really wish I could find a chart that is reputable about the shelf lives of ALL oils. I LOVE my hazelnut oil but now I'm worried about the sale of my products containing such a short shelf life. PLEASE HELP SUZAN!!!

Amanda Dvorak said...

And Hemo seed 2 YEARS??!! I think they have there information wrong. Or am I wrong??

Susan Barclay-Nichols said...

I think you need to ask the Soap Queen where she gets her numbers as I have no idea what her research materials might be. I have a whole section on emollients that I would refer you to, including the oil comparison charts I painstakingly put together for situations just like this. I'm not comfortable answering questions on other people's work. If you want to know my sources, take a look at the FAQ. I list my texts there.

Amanda Dvorak said...

Thank you, I will ask. Maybe it's for BB products in particular, I'm not sure but I will ask. I'll re review you chart. Thanks again Susan

Kat Jo said...

I have a strange question. We have very high minerals in our well water, especially copper. This is a constant battle with my blonde hair turning green. I use a Redken product once or twice a week to remove the green which works well but is a process of letting it sit on my hair for a half hour and then washing several times. Anyhow, this product contains EDTA as one of the first ingredients. I purchased some powder EDTA with the idea of adding it to my daily shampoo to hopefully keep the green from ever starting. Is this a reasonable idea or could adding the EDTA destroy my hair? I'm thinking that this would turn my regular shampoo into a strong chelator but I'm afraid to make matters worse. Could I maybe make a daily rinse, add it to conditioner or should I just stick with the expensive Redken?

Susan Barclay-Nichols said...

Hi Kat Jo. Sure, give it a try. You don't need much, and I don't suggest going over the manufacturer's suggested usage rates for the version you buy. I don't think the suggested usage rate will hurt your hair, but keep good records about the product you make and the product when you are using it.

As a question from someone who knows little to nothing about wells, isn't there something you could do to the well to stop the metals coming through? It can't be good to have that much copper for drinking, could it?

Kat Jo said...

It is not good, the levels are actually too high to drink so we use bottled water. I only recently found out about the levels and now we're trying to find a solution. We have several filtration and softening systems already so our water guy thinks it may be the copper pipes. Our house is only 9 years old so it's killing me to think about replacing them all but it might come to that. I know there is a giant reverse osmosis system that costs a fortune that could likely help but I'm not sure if the copper has been pulled from the pipes then they might need to be replaced anyway....it's a mess so yeah, I'm taking it little by little and starting with what I can do, my green hair!

Niki1695 said...

Hi Susan, I have seen you mentioning in couple of posts that grapeseed oil has 3M shelf life. Gracefruit.com sells grapeseed oil with 12M shelf life: http://www.gracefruit.com/butters-oils-and-waxes/liquid-oils/grapeseed-oil.html, naturallythinking.com 14-16M shelf life: http://www.naturallythinking.com/grapeseed-carrier-oil.html, manske-shop.com 12M: http://www.manske-shop.com/Oele-Butter-Wachs-konventionell/Oele/Traubenkernoel-raffiniert/TRAUBENKERNOeL-raffiniert-777.html. It might help some of those located within EU to use this lovely oil in their creations :-).
Niki

Lilys Lotion said...

Hello Susan, I need HELP. I purchased Disodium EDTA to incorporate into my Goats Milk Lotion for Personal use. I currently have a lotion formula that I use in which the PH is around 7.5. Now I'm not sure what will happen to the PH when I add the Goats milk powder to my formula but I was wondering if you could give me some insight. If I add the disodium EDTA at the recommended usage rate into my water phase along with the goats milk powder is this a good option. Or should I use the Tetrasodium EDTA. THANK YOU for any input!

Susan Barclay-Nichols said...

Hi Niki1695! I'm really not sure how they do that, unless they are adding a lot of anti-oxidants to the product. I would love to have the ability to do a test on the oil over a period of time to see what happens, but that isn't something I could do!

Hi Lily's Lotion! Why are you using EDTA in the first place? Why is the pH of your lotion so high? How are you measuring it? What is the pH of the powder? There are just so many questions i have to be able to help!