The main body of the vial is composed of borosilicate glass, which has a high chemical compatibility with most chemicals. The only chemicals that are not compatible with this areare hydrofluoric acid and concentrated hydroxide solutions. The septa within the cap assembly acts to seal the contents of the inside the vial, and is the only other part that will come in direct contact with the solution. PTFE has excellent compatibility with almost all materials with the exception of: diethyl amine, some alkali metals, fluorine, and other strong fluorinating agents.
The silicone backing of the septa and the polypropylene cap should not come into direct contact with the stored material. However, when storing solvents, vapours may escape from the vial over time. As Ossila's vial caps are made of virgin grade polypropylene, the vapours from most common solvents will not cause the cap to dissolve. This stops the vial lids from welding to the glass when storing solvents for extended periods of time.