A GC system (Agilent GC 7890A, USA) and an automatic headspace sampler (DANI HS 86.50, Italy) were used for the HS-GC measurement. The GC system was equipped with a flame ionization detector and a DB-5 capillary column (30 m long, 0.35 mm ID) operating at a temperature of 30 °C for 2.8 min with nitrogen carrier gas (flow rate = 3 mL/min).