Cosmetics Ingredients are not all the same
As a beginning chemist, one of the most frustrating things for me as I started my career was the product ingredient lists. While all the products had cosmetic ingredient listings, the ingredient were rarely things that I learned about in college. The cosmetics industry just does not use the same naming system for ingredients as the one you learned in college. 
The college system of naming is the IUPAC system. The great thing about this system is that it allows you to figure out the chemical structure of any material from its name alone. Unfortunately, it also leads to incredibly long names for the ingredients so it isn’t practical to use it for naming cosmetics.
The cosmetic system is the one created by the PCPC and listed in the INCI Dictionary. They use a whole different set of naming conventions which lead to shorter names but also make it impossible to ascertain most ingredients structures from the name. Oh well, you don’t really need to know the molecular structure to be a good cosmetic chemist.
Ingredients are not the same
One of the things I wanted to point out in this post is that not all ingredients are the same even if they have the same name. To understand why, let’s look at an ingredient like Sodium Lauryl Sulfate (SLS).
SLS is a pretty straightforward molecule. It is a surfactant with a 12-carbon chain backbone attached to a SO4 group and ionically bonded with a sodium ion.
But when you buy Sodium Lauryl Sulfate from one supplier, you might not be getting the same chemical as when you buy your ingredients from another supplier. Why?
It turns out that this is because of the way sodium lauryl sulfate is produced. To create SLS, you react Lauryl Alcohol with Sulfur Trioxide gas. This is further neutralized with Sodium Hydroxide to produce SLS. The key part of this reaction is the “Lauryl Alcohol” and the way that it gets produced.
Lauryl Alcohol
Lauryl alcohol can be obtained from a number of sources including from the fatty acids of plant oils and crude oil. Unfortunately, these sources are a mixture of fatty acids and it is incredibly difficult to isolate only the C12 molecules. So, instead of starting the production of SLS with pure Lauryl Alcohol, most companies start with a mixture that is mostly Lauryl Alcohol but contains a number of other residual fatty alcohols.
Therefore, the chemical properties and quality of the SLS will vary from raw material supplier to raw material supplier depending on the quality and type of starting material for their SLS. The more pure the starting Lauryl Alcohol source, the better controlled the SLS end properties will be.
This same thing applies to most any other cosmetics ingredients that you might use. It’s pretty rare that a cosmetic ingredient is pure. It is nearly always a mixture of the main ingredient you want and some residual ingredients that you might not.
