Analysis of Volatile Chemicals in the Extracts. The volatile
chemicals in each extract were identified by comparison with the
Kovats gas chromatographic retention index (KI)15 and by the mass
spectrometry (MS) fragmentation pattern of each component
compared with those of authentic chemicals. An Agilent model 6890
GC equipped with a 30 m × 0.25 mm i.d. (df = 0.5 μm) DB-WAX
bonded-phase fused-silica capillary column (Agilent, Folsom, CA) and
a flame ionization detector (FID) was used for measurement of KI and
routine analysis of volatile chemicals. A 30 m × 0.25 mm i.d. (df = 0.5
μm) DB-1 bonded-phase fused-silica capillary column was also used
for measurement of KI. The helium carrier gas flow rate was 1.0 mL/
min at a split ratio of 20:1. The injector and detector temperature were
260 and 290 °C, respectively. The oven temperature was programmed
to increase from 50 to 210 °C at 2 °C/min and then held for 93 min.
The concentration of each chemical was calculated using a previously
reported method.16