Yes, polypropylene as a vial material is a good choice for protein analysis because normal borosilicate glass vials are known to adosrb some types of analytes such as proteins, peptides, and amines. This leads to lower recovery and is caused by silanols on the glass surface. Polypropylene does not have these groups and therefore adsorption is not an issue with these vials.
It is important to note that some plastic vials are made in high speed machines and contain a lot of “mold release agents”. These vials would not be suitable for many proteins as the extractables could cause damage to your samples. Also, these agents could also cause erroneous peaks in LCMS. The Mass Spec compatible vials are most suitable as they are not made in high speed machines and we avoid the use of “mold release agents” making them more suitable for proteins and minimizing extractables.