VG (vegetable glycerin) is a marketing name that means nothing regarding the purity of glycerin (glycerol).
I'd rather use Glycerin USP. It's pharmaceutical grade glycerin. USP means it meets specifications of United States Pharmacopeia.
Glycerin USP is US pharmaceutical grade glycerol. Call it VG if you want to.
As an example, the Glycerin USP sold by Walmart and CVS are both made by Humco. Both are the highest quality pharmaceutical grade sold in the USA. Both have the highest quality bottles, caps and airtight seals and will maintain USP specifications even if stored unopened at room temperature for up to five years.
IMPORTANT. The words Glycerin USP appear on the bottle if it is Glycerin USP. The wording and spelling must be exact to be Glycerin USP. Other words may not appear between the words Glycerin and USP on the label, if they do it's not Glycerin USP. The word pure also appears on the CVS bottles, but in this case the word is meaningless.
The minimal purity for Glycerin USP is 99.5%. The remaining .5% is water: not gasoline, arsenic or orange juice. In practice the Humco Glycerin USP is produced at a higher level of purity than 99.5% in order to assure high quality control of the product.
The Humco Glycerin USP has a lot number and an expiration date printed on every bottle. If your VG doesn't, it isn't Glycerin USP. The unopened expiration date can be as long as five years for the Humco product due to superior bottling methods.
Anyone can buy a tank car or a 55 gallon drum of Glycerin USP and run off a lot of gallon bottles of the stuff for sale cheap. Unless the repackaging is done in a clean room with hermetically sealed equipment and sealed containers the repackaged product can not be sold as Glycerin USP. It can't have the five year expiration date either because it's been exposed to open air. However, the seller can claim the contents were Glycerin USP at the time the bottle was filled. This type of product is often sold as food grade and should be used up within 12 to 18 months whether opened or not, just like any Glycerin USP that has been exposed to open air. These products are usually sold in plastic jugs with cheap caps. I suspect this product is fine for
vaping so long as it's all used up within a year or stored with minimal exposure to air/oxygen in a freezer.
For my Glycerin USP, I just buy the CVS (Humco) product and store it unopened in the cupboard for up to five years. I keep the opened bottle in the refrigerator or freezer and use it up within one year. The high quality nicotine base I get from Xtreme Vaping is made with Glycerin USP base. I store nicotine base in the freezer in amounts that I'll use up within 18 months.
