I've seen a number of threads here asking about VG/PG and if there are different qualities like with nicotine. I am posting this hoping to answer those questions to the best of my knowledge.
I am not a professional chemist; I started out in school as a chemical engineering major before switching to CSE (didn't like the memorization). I have 3 years college level honors chemistry & organic chemistry, as well as thousands of hours in laboratory environments. I am not clueless, but don't take what I say as gospel.
First, a couple of terms:
USP - United States Pharmacopeia. This is an organization that sets industry standards for purity with pharmaceuticals behind and over the counter as well as non-food consumables. Think of them as the legislative counterpart to the FDA. They publish all those purity standards in a master list every year.
USP grade - A chemical meeting the purity/quality standards set by the USP organization. A small sample is sent for testing before a batch can be labeled as USP grade.
Glycerin - The commercial name for the chemical glycerol (IUPAC name 1,2,3-propanetriol).
Glycerin can be two ways: it can be extracted from fats and oils or it can be produced synthetically.
Extracting from oils: Triglycerides are extracted from fats and oils and then the ester groups are removed, leaving glycerol. They then purify this into the final product (usually through distillation).
Synthetically: Normally this is done from propylene or propene. It is converted to glycerin usually through a 3 step process. The TL;DR of the (standard) process is: propylene is chlorinated, oxidized, and then hydrolyzed to form glycerin.
Glycerol/Glycerin/Glycerine extracted from fats and oils is chemically identical to synthetically produced Glycerol/Glycerin/Glycerine.
As for PG:
Propylene glycol (IUPAC name Propane-1,2-diol). It's produced through synthesis. There is no real competing industrial process, so I'll leave it there.
It, too, is subject to the same USP quality standards as VG.
Now, on to the important stuff.
What the heck does it all mean and why does it matter?
USP grade = USP grade = USP grade. Any USP grade glycerin or propylene glycol is the same quality as any other USP grade glycerin or propylene glycol.
99.5% purity and above = USP grade. Some places will add distilled water and you'll have 99.5% USP grade glycerin and .5% distilled.
The only impurities in any USP grade glycerin will either be introduced in the bottling process.
So, you might be able to get .5% more pure in certain places, but in the end you won't notice that quality difference.
A few caveats:
If you're allergic to PG, it may be worth making sure that the glycerin you are buying is VG, not because it's any different but synthetically produced glycerin may be made in the same facility as where it is bottled. This means there can be propylene impurity introduced in the bottling process.
Some people have reported extreme nausea from using CVS glycerin. I can not say anymore on it, because I can't be sure the claims are real or related to the glycerin.
If I am wrong on anything, please correct me. I will edit it into the post. I am just trying to help people get the proper information.
Edit: I edited this to clarify one thing I've said: USP glycerin is, at bottling, the same as any USP glycerin. Though the bottling process and 'chain of custody' (handling process) can affect the overall quality. I.E. the initial product is pure, but when it reaches the consumer, it can be less pure. Just to reiterate this: buy from a reputable vendor.
Very nice, thanks for the write up. I think this could really help some people. The only point that I would expand on:
> USP grade = USP grade = USP grade. Any USP grade glycerin or propylene glycol is the same quality as any other USP grade glycerin or propylene glycol.
while it may be of the same purity, it can vary quite a bit based on what it is derived from. I think this is important, and if I had my wishes, would love to see the USP designation split to clearly identify if its produced solely from vegetable product, animal, or a mix of the two.
example : the VG I choose is marketed as 100% palm oil derived. however there is no standard for this. I would like to see one, so this marketing point can be substantiated.
I don't have any real reason to be concerned with this, but would just prefer to use a 100% vegetable sourced glycerin for my vaping needs.
not that you are wrong, just more info to add to that point.
oh, one last thing to add : I cannot find the source, but I believe that once USP Grade glycerin is opened, its not longer considered USP grade, rather it is now food grade due to exposure to the air and its hygroscopic nature, it will absorb impurities from the moisture in the air in unknown quantities.
Ah, I thought the USP certification aliquot was sent from the batch and then bottled.
As for the variation, my reading said that no matter from what it is derived, that the resulting glycerine was chemically identical. Could you elaborate on that?
Hey yeah, from my reding too the end reality is chemically identical. I just like the idea that it can made from plants, which I believe are infinitely cheaper to create than the animals that the fat is processed into VG. Plants need water and sun. And produce oxygen while they are alive. Animals need food and water,typically need more care, and produce more co2 over their life.. Just a personal choice in my case.
Since you seem to be versed in the quality of VG, what is your take of Capellas VG? http://capellaflavordrops.com/VegetableGlycerinGallon.aspx
Is it USP?
It doesn't say, so i have no idea. But at $40/gallon, I wouldn't spend the money on it.
Recently, essential depot was selling 2 gallons for $50 no shipping. Might still be going on. Amazon has $40/gallon VG no shipping that is USP grade and says it on the label.
So to get this straight, you would have no problem vaping any USP grade glycerine? I have some 100% usp glycerine from a local pharmacy and it doesn't say vegetable anywhere, should I not give a crap?
technically there is no such thing as "usp vegetable glycerin" this is because USP designation states it has to be labeld by the USP monograph. this is a very specific language that must be used for it to adhere to their standards.
as such, it must be labeled either: glycerin, USP. or USP Glycerin.
copied from a page on e-cig forum dot com (NOT MY WORDS, BLATENTLY STOLEN) :
There is no Vegetable Glycerin monograph in the USP because the USP considers it’s purity standards for Glycerin to be adequate for human use(regardless of source). However, some people insist on utilizing Vegetable source products for allergenicity(pig or porcine allergy), religious(Orthodox Jewish & Muslims) or ethical reasons.
Although I cannot speak for EVERY manufacturer of Glycerin, USP that exists, I did personally speak to the Quality Assurance person at Humco, Inc. Humco contract packages (meaning, places their manufactured product into other company's labeled bottles) for almost every major pharmacy label in the country. From their company information they contract package for the following:
Among our wholesale customers are McKesson Healthcare Solutions, Cardinal Health and AmerisourceBergen(which is the Family Phamacy and Good Neighbor Pharmacy labels) along with most regional wholesalers. In addition, Humco supplies products to Walgreens, CVS, Rite Aid and Wal-Mart.
So any Glycerin, USP labeled in any of the above mentioned Pharmacy labels (Humco, Family Pharmacy, Good Neighbor Pharmacy, CVS, Rite Aid, Walgreen's and Walmart labels) IS USP grade AND Vegetable sourced.
Brands of Glycerin, USP not included in the above list would have to be verified as solely vegetable source by direct contact with the manufacturer/packager/distributor listed on the label.
Is there some certification process for transferring the glycerin from one container to another? Does it stay USP when it's transferred if they're not taking samples from the new container? How many companies actually have their stuff certified USP and don't just pump it from a USP 55 gallon drum and slap USP on it. I don't expect answers to all those questions, just things that I wonder about.
yes
no
good question, probably quite a few (sadly) just pump it into a different container and give it a label.
/u/Vigg-o-rama was telling me that once unsealed, it is no longer USP. Most places are going to be bottling it themselves and then selling to resellers. I.E. Humeco makes and bottles glycerin, then sells it to Walmart and CVS who stick their label on it and sell it.
I should have been more specific. I really meant some mom and pop place that will sell you some USP grade VG from their 55 gallon drum, but what you are buying is technically food grade since they broke the seal on that drum and dispensed into a bottle, for you to buy.
<3 this is gold. Thanks brother!!!!!!!
However I would like to revisit this statement: USP grade = USP grade = USP grade. Any USP grade glycerin or propylene glycol is the same quality as any other USP grade glycerin or propylene glycol.
FALSE!
While USP is a MINIMUM quality standard, numerous other factors that fall upon the chain-of-custody of the ingredient can have MAJOR effects on the quality of the end product. I.E. hygration of the material :) It may be labelled USP but the handler or packager might not be licensed to relabel as USP product and therefore might be lackluster in vaporizer performance
Just a keen thought :)
EDIT - /u/vigg-o-rama already has a nice start on this topic
I am a bit confused on this part specifically. I had noted that impurities can be introduced during the bottling/storage/shipping/handling, but the discussion with /u/vigg-o-rama led me to believe that it is no longer USP grade once the seal is broken.
Hygration, do you mean hydration or is that a process with which I'm unfamiliar? I know that some places dilute with a small bit of DI to make it easier to bottle, and of course you have to worry about storage of the DI, age, etc.
HA! as a reef aquarium hobbyist I can tell you more than you ever really wanted to know about DI... lets just say that the DI anyone is adding to VG to thin it out, is not as pure as you would like it to be.
True revere osmosis deionized water is very "aggressive" just like the VG, it doesn't want to be pure, it wants to pull in things (contaminants) from the environment around it. so true chemically pure RO/DI H2O is also very difficult to maintain its purity. unlike the VG, it doesn't want to absorb water, but rather any contaminant the surface comes in contact with. as a real world example : I used to have my cat litter boxes in the same room as my RO/DI. I would make up a batch of what should be chemically pure water, and test it. yup, pure.. leave it sitting in the room with the cat boxes long enough, and it has absorbed ammonia from the air that the cat boxes were giving off. by long enough, I mean a few days, and while it was negligible, it was a testable amount of ammonia.
as /u/nudenicotine has stated, hygration is a property of VG that makes it want to absorb any h20 it can from its surrounding environment. as we live in a world that has humidity, it can readily pull this h20 from the surrounding air.