*2.3. Chemical Standards and Standard Solutions*

Methanol, water, and n-hexane were of HPLC grade purity (Sigma-Aldrich, St. Louis, MO, USA). Pure chemical standards of volatile compounds and phenols were purchased from AccuStandard Inc. (New Haven, CT, USA), Acros Organics (Geel, Belgium), Alfa Aesar (Haverhill, MA, USA), Cayman Chemical Co. (Ann Arbor, MI, USA), Extrasynthese (Genay, France), Fluka (Buchs, Switzerland), Honeywell International Inc. (Morris Plains, NJ, USA), Merck (Darmstadt, Germany), and Sigma-Aldrich. Standard solutions of volatiles were prepared in refined sunflower oil and that of phenols in pure methanol.
