2.1 Chemicals and materials
PAH calibrants were prepared from NIST SRM 1647f (16 EPA PAH in acetonitrile) purchased from Promochem (Wesel, Germany). Cyclohexane and diethyl ether were picograde and obtained from Promochem. Surrogate standard mixture PAH-Mix 9 was from Dr. Ehrestorfer (Augsburg, Germany) and contained the deuterated 16 EPA-PAH in cyclohexane. Stir bar sorptive extraction (SBSE) devices (polydimethylsiloxane, 10 mm x 0.5 mm) were obtained from Gerstel (Mülheim an der Ruhr, Germany). Orbo-1000 polyurethane foam (PU foam) cartridges (22 mm outer ∅ x 7.6 cm) containing 0.022 g PU foam cm-3 and matching quartz filters (3.5 mm ∅) were purchased from (Supleco, Mainz, Germany) and received in amber glass bottles.