High capacity headspace (BF-1112, Beijing Bafang Century Corporation, China), with 2000 mL capacity and 160 mm I.D., was made from stainless steel. The inner surface was polished to ensure low adsorption. A stand-off stainless steel tray, containing one 140 mm diameter disc and three 40 mm long legs, was placed in the chamber of the headspace. There are two ports in the top lid, with one as inlet port and the other as sampling port for SPME. The headspace was sealed by a polytetrafluoroethylene septum between the stainless steel body and the top lid.