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G
olay
&
M
oulin
:
J
ournal of
AOAC I
nternational
V
ol
.
99, N
o
.
1, 2016
215
qualitative
cis/trans
C18:1 FAME isomers standard mixture
solution,
D
(
k
). The resolution is sufficient when resolution (R)
criteria is equivalent or higher than 1.00 (Figure
2012.13C
).
The following two examples report applicable conditions for
a correct separation of
cis
and
trans
with different GC injectors.
(b)
Example 1.
—Split injection mode.
(
1
)
Column.
—100 m length × 0.25 mm id, 0.2 μm film
thickness, fused silica capillary column.
(
2
)
Stationary
phase
.—Cyanopropyl-polysiloxane
or
equivalent polarity.
(
3
)
Carrier gas type.
—Helium.
(
4
)
Column head carrier gas pressure.
—225 KPa
(175–225 KPa).
(
5
)
Split flow
.—25.5 mL/min.
(
6
)
Split ratio.
—10:1.
(
7
)
Injector temperature.
—250°C.
(
8
)
Detector temperature.
—275°C.
(
9
)
Oven temperature program.
—Initial temperature
of 60°C, maintained for 5 min, raised at a rate of 15°C/min up
to 165°C, maintained at this temperature for 1 min, and then
raised at a rate of 2°C/min up to 225°C for 20 min.
(
10
)
Amount of sample injected.
—1.0 μL.
An example of the GC profile obtained with these conditions
is reported in Figure
2012.13A
.
(c)
Example 2.—
On-column injection mode.
(
1
)
Column
.—100 m length × 0.25 mm id, 0.2 μm film
thickness, fused silica capillary column.
(
2
)
Stationary
phase
.—Cyanopropyl-polysiloxane
or
equivalent polarity.
(
3
)
Carrier gas type.
—Hydrogen.
(
4
)
Column head carrier gas pressure.
—210 KPa
(175–225 KPa).
(
5
)
Injector temperature.
—Cold.
(
6
)
Detector temperature.
—275°C.
(
7
)
Oven temperature program
.—Initial temperature
of 60°C, maintained for 5 min, raised at a rate of 15°C/min up
to 165°C, maintained at this temperature for 1 min, and then
raised at a rate of 2°C/min up to 225°C for 17 min.
(
8
)
Amount of sample injected.
—1.0 μL.
An example of the GC profile obtained with these conditions
is reported in Figure
2012.13B
.
(d)
Resolution between C18:1
trans
and
cis
.
—Inject into the
gas chromatograph 1.0 μL calibrating solution,
D
(
k
). Determine
peak width at half height and distance between the left of the
Figure 2012.13C. Example of a GC chromatogram (i.e., with insufficient and sufficient resolution for C18:1
trans
).
199