The detergent being used by BP, up until recently, was Nalco's Corexit EC9527A. Nalco is a large company that makes specialty chemicals including detergents and surfactants. It contains three ingredients, a solvent we call EB ethylene glycol monobutyl ether, a sulfonic acid detergent, and a few percent of propylene glycol.
The sulfonic acid detergent is secret, but it is likely to be an ethoxylated/propoxylated version of lauryl sulfonate -- probably naphthalene sulfonate, but possibly toluene sulfonate or benzene sulfonate. The presence of propylene glycol in the product leads me to believe they propoxylated the detergent.
This detergent is pretty generic, and it is hard to believe it would that dangerous. The MSDS has a few hazards that are mostly due to the irritation that a concentrated detergent would have on the eyes or skin. There are hazards due to the EB, which has some liver and reproductive side effects. (Probably not the greatest choice, but I suppose its cheap.)
EPA has a long list of approved dispersants for cleaning up oil spills. It is important to note that Corexit EC9527A is on the approved list. [24-May-10 update: BP has been using a blend including Corexit EC9500, which has the same active ingredient as EC9527A, or so we think.]
(1:10 Product-to-No. 2 Fuel Oil ratio)
(LC50 values in ppm)
|DISPERSIT SPC 1000™||7.90||8.20||40.00||100.00||73.00|
|FINASOL OSR 52||5.40||2.37||32.50||71.60||52.10|
|MARE CLEAN 200||42.00||9.84||63.97||84.14||74.06|
|SEA BRAT #4||23.00||18.00||53.55||60.65||57.10|
|SEACARE ECOSPERSE 52 (see FINASOL® OSR 52)||5.40||2.37||32.50||71.60||52.10|
|SEACARE E.P.A. (see DISPERSIT SPC 1000™)||7.90||8.20||40.00||100.00||73.00|
|SF-GOLD DISPERSANT (see SAF-RON GOLD)||9.25||3.04||84.80||53.80||69.30|
|ZI-400 OIL SPILL DISPERSANT (see ZI-400)||8.35||1.77||50.10||89.80||69.90|
|Mysidopsis Bahia - a shrimp used in toxicity testing|
|Menidia Beryllina - the Inland Silverside|
Wikipdeia reports that BP is ordering multiple truckloads of Dispersit SPC 1000 from US Polychemical. US Polychemical does not provide any detailed Chemical. A government filing says it is a mixture of nonionic and anionic surfactants, which is not very helpful at all. This seems to be one of those industries where everyone keeps secrets from competitors, but I suspect all the products on the market are basically the same.
According to the table above, the new dispersant Dispersit SPC 1000 is much more effective against South Louisiana crude, but also more toxic than Corexit EC9527A.
Overall, I am glad to see that there actually is marine testing on these dispersants. I think that dispersants help more than they hurt, and that there is no way that this massive oil spill is not going to have a massive harm on the environment. Choice of dispersants can direct that massive harm one way or another. So far, we seem to have escaped severe damage.
Update 31 May 2010
Nalco has issued additional info on Corexit EC9500, which is now being used in place of EC9527A. They claim it is a blend of six ingredients. On its MSDS, it has three ingredients that add up to about 45% of the total composition. Ordinarily you'd say the rest was water, but it is hard to say. A Nalco press release says that there are six ingredients, and then in crossword puzzle fashion gives clues as to what they are:
• One ingredient is used as a wetting agent in dry gelatin, beverage mixtures, and fruit juice drinks.
• A second ingredient is used in a brand-name dry skin cream and also in a body shampoo
• A third ingredient is found in a popular brand of baby bath liquid.
• A fourth ingredient is found extensively in cosmetics and is also used as a surface-active agent and emulsifier for agents used in food contact.
• A fifth ingredient is used by a major supplier of brand name household cleaning products for “soap scum” removal.
• A sixth ingredient is used in hand creams and lotions, odorless paints and stain blockers.
Let's guess what they might be:
1. Probably the main surfactant, I believe an a fatty alcohol sulfonate -- probably ethoxylated
2. Is a petroleum distillate or a fatty alcohol-- which must be there for package stability
3. Is the propylene glycol
4. Appears to be a secondary surfactant. I am going to guess it is an EO/PO alcohol, where EO/PO stand for a block copolymer of ethylene oxide and propylene oxide.
5. Is a water softener - certainly a non-phosphate type. It could be an polyacrylic acid type or many other things.
6. Is a solvent, perhaps the petroleum distillate disclosed on the MSDS.
Having done all this guessing, anyone with a sample and a lab could figure this out in less than a day. The only people in the dark are 300 million Americans. All the competitors could analyze this right away. There is no reason they should not be disclosing the composition in full detail, except as feeble attempt to confuse BP's purchasing agents.