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Figure 1
Excellent response and resolution of PAHs at 5pg on column in SIM mode
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4
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2008 vol. 1
Environmental
Method Parameters
For our SIM method we chose to use the new Rxi®-5Sil MS column. This stationary phase incorporates phenyl rings in the polymer
backbone, which strengthens the siloxane chain, preventing thermal breakdown. This low bleed column is similar in selectivity to
5% diphenyl/95% dimethyl phases, but offers improved signal-to-noise ratios, resulting in increased sensitivity and subsequently
lower detection limits. The silarylene polymer not only exhibits improved thermal stability and reduced bleed, but it also shows
improved separation for aromatic compounds, such as PAHs.
Analytical conditions were set to optimize resolution of critical pairs and reduce discrimination of high molecular weight analytes.
We chose a 4mm Drilled Uniliner® inlet liner with wool, since direct injection using this liner provides near complete transfer of
sample analytes to the column. To improve the quantification of high molecular weight compounds we chose a thin film thickness
(0.25µm) and set the injection port temperature to 300°C. A pulsed splitless injection technique was used to maximize the transfer
of analytes onto the column. The pressure pulse is an effective injection technique for trace level analyses and also helps minimize dis-
crimination against the high molecular weight components. Finally, the ion source and quadrupole temperatures were set at 290°C
and 180°C, respectively. This increase in detector temperatures, from the defaults of 230°C and 150°C, yields better peak shapes and
responses for the PAHs.
Peak List
Retention Time
1. naphthalene
4.93
2. 2-methylnaphthalene
5.58
3. 1-methylnaphthalene
5.68
4. 2-fluorobiphenyl (s)
5.93
5. acenaphthylene
6.45
6. acenaphthene
6.62
7. fluorene
7.12
8. phenanthrene
8.06
9. anthracene
8.11
10. fluoranthene
9.23
11. pyrene
9.45
12.
p
-terphenyl-d14 (IS)
9.61
13. benzo(a)anthracene
10.65
14. chrysene
10.69
15. benzo(b)fluoranthene
11.96
16. benzo(k)fluoranthene
12.00
17. benzo(a)pyrene
12.42
18. perylene-d12 (IS)
12.51
19. indeno(1,2,3-cd)pyrene
14.19
20. dibenzo(a,h)anthracene
14.23
21. benzo(ghi)perylene
14.65
Column:
Rxi
®
-5Sil MS, 30m, 0.25mm ID, 0.25µm (cat.# 13623)
Sample:
PAH mix, 1µL of 0.005µg/mL (IS 2µg/mL)
SV Calibration Mix #5 (cat.# 31011)
1-methylnaphthalene (cat.# 31283)
2-methylnaphthalene (cat.# 31285)
2-fluorobiphenyl (cat.# 31091)
Inj.:
1.0µL (5pg on-column concentration),
4mm Drilled Uniliner
®
(hole near top) inlet liner (cat.# 21055-200.5),
pulsed splitless: pulse 20psi @ 0.2 min., 60mL/min. @ 0.15 min.
Inj. temp.:
300°C
Carrier gas:
helium, constant flow
Flow rate:
1.4mL/min.
Oven temp.:
50°C (hold 0.5 min.) to 290°C @ 25°C/min. to 320°C @ 5°C/min.
Det.:
MS
Transfer line temp: 290°C
Ionization:
EI
Mode:
SIM
GC_EV00970
Full Scale
Accurately Quantify PAHs Down to 5pg On-Column
Continued from page 3.
Single ion monitoring (SIM) program
Group Time
Ion(s)
Dwell (ms)
1
4.00
128
100
2
5.25
142
100
3
5.80
172
100
4
6.25
152
100
5
6.90
166
100
6
7.60
178
100
7
8.75
202, 244
100
8
10.2
228
100
9
11.5
252, 264
100
10
13.5
276, 278
100
Outstanding
response at 5pg
on-column!