2.2.1. Standards and Reagents

The reference standard benzene (99.96%), toluene (99.93%), ethylbenzene (≥ 99.90%), p-xylene (99.90%), and benzene-d6 (99.99%), the latter used as internal standard (IS), were purchased from Sigma Aldrich. The reagents methanol and propylene glycol used for the preparation of standard/calibration solutions, as well as blank and samples solutions of a purity grade of more than 99%, were purchased from Sigma Aldrich.
