Polypropylene is chemically resistant and the material of choice for pH sensitive samples, sodium or heavy metal analyses.
The PP vials are ideal when working with pH sensitive samples, aqueous samples in pharmaceutical applications, or undertaking sodium analysis.
If you’re analyzing anything that might adsorb into borosilicate glass, or looking to avoid sodium adducts pulled out of glass, these vials seem to do the trick. Using them on triple quad mass spec quite successfully.