Can exposure to oxygen cause nicotine levels in e-liquids to drop? The answer is yes and no. Technically e-liquids that are used for cartridges and refillable bottles used with devices can go bad. This is fairly easy to avoid, because most e-juices have an expiration date and maintain shelf lives of 1 to 2 years easily. When past the listed expiration date, the quality of e-liquids becomes questionable. Also the ways such products are stored and cared for can diminish the liquid's strength.
With that said, here are the main problems caused by improper storage and oxygen exposure for e-liquids on the market today. Hopefully this information will be helpful to readers and retailers out there.
General Storage Problems
Most quality e-liquid manufacturers package their products in tinted glass bottles to avoid contamination and provides extended shelf life. General storage is important with all liquid products, because their flavors are very susceptible to heat exposure and various chemical reactions. Leaving liquids exposed to direct sunlight is a particularly bad idea. Even leaving such products in bright light can have adverse effects on the nicotine concentration and cause flavoring to evaporate. This is true of Propylene Glycol (PG), Vegetable Glycerin (VG), alcohol, and water-based flavor cartridges. In the very least, such exposures can cause a break down of the e-liquid elements, causing permanent sedimentation. Such sedimentation does diminish the nicotine levels somewhat and spoils the juices more rapidly. While this is not highly dangerous, it does make the product ruined for general usage and should be thrown away.
The best way to avoid general storage problems is to keep the bottles in a properly cooled storage place such as your drawer, in a box or in on shelf will do normally. (NOTE: Avoid refrigeration if possible as that can have negative effects to the bottled liquids.)
Oxygen Exposure Problems
Exposure to the air has adverse effects on e-liquids of all kinds. Such exposure causes oxidation, a process that begins when air comes in contact with any liquid. The liquids begin to oxidize, which means spoiling and decaying of the e-juice. Although this process generally takes a long period of time to develop, vapers should avoid leaving bottles open for any amount of time unnecessarily. A properly sealed e-liquid bottle or vape cartridge can last well over a year or more, but an opened one should last slightly less than a year in a properly stored environment. Oxidation causes the liquid's flavor and color to change over time. This is indicated by a darker shade of color in the product tint. There can be a change in odor, but this is less likely to occur in normal storage circumstances.
There are some that think that oxygen exposure causes e-liquid nicotine levels to diminish or drop. There is no evidence to support the idea that oxygen exposure drops or diminishes nicotine content in e-liquids, but overly oxidized products will usually taste bad and should not be used.
So can exposure to oxygen cause nicotine levels in e-liquids to drop? In reality, this isn't true. Open air exposure causes the flavors to go bad, long before loss of nicotine strength would ever happen. It is exposure to light or high temps that causes nicotine levels to diminish. Even products slightly past their labeled date of expiration should not be harmful or lose their overall potency. Still, the best idea is to always keep your bottles sealed tightly and stored in a cool dark place, but also check their freshness by observing the expiration dates.
It is very common for vapers to become misinformed about products and their usage in the open marketplace. The idea that oxygen exposure causes nicotine levels to drop in e-liquids is one such modern myth, so don't believe the hype. Do your research will keep your choices well informed as a consumer and self-assured as a buyer, no matter what you are shopping for in the global marketplace.