Analytical Protocol of GC-MS
An Agilent 6890N GC with an Agilent 5973I MS operated
in electron impact mode was used for sample analysis.
The
capillary column was an HP-5 ms (30 m×0.25
mm×0.25
µm). The
initial oven temperature was 50ºC, held
for
1 min, then raised to 280ºC at 10ºC/min with a final
isotherm
of 5 min. The
injection port and interface temperature
were both 280ºC. One microliter of sample was
injected
in the splitless mode. Helium carrier gas was maintained
at a constant flow rate of 1 ml/min. The
ionization
source
temperature and the MS quadrupole temperature
were
set at 230ºC and 150ºC, respectively.
To
identify the
phenolic
compounds, the MS was operated in full-scan
mode,
mass fragments of the components were firstly compared
to the mass fragmentation data contained in the NIST
02
and then compared to that of the authentic standards for
final
confirmation. For quantitative analysis, the MS was
operated
in selected ion monitoring (SIM) mode. The
ions
monitored
for each compound are listed in Table
1. The
pretreated
standard solutions with different
known concentrations
were determined to plot the standard curves (Table
2),
based
on which contents of the four phenolic compounds
extracted
from plant tissues and plant exudates were calculated.