Optimized Polycyclic Aromatic Hydrocarbon (PAH) Analysis by GC-MS

• Rxi-SVOCms column provides good separation and response for critical environmental PAH compounds.
• Low column bleed ensures accuracy for late-eluting target analytes.
• Split injection SIM analysis minimizes inlet discrimination.

Polycyclic aromatic hydrocarbons (PAH) are ubiquitous environmental contaminants that form both naturally and due to human activities, primarily through the incomplete combustion of carbon-containing materials. Because some polycyclic aromatic hydrocarbons are carcinogenic, trace-level monitoring of air, water, and soil samples is essential for assessing exposure. PAH analysis by GC-MS using an Rxi-SVOCms column under the optimized conditions shown below provides effective detection of the most relevant compounds.

Using SIM mode and split injection to minimize inlet discrimination for a challenging coal tar sample, good chromatographic performance was seen for a range of PAH compounds. Volatile early eluting compounds exhibit good peak shapes and responses while low column bleed minimizes background interference and improves sensitivity for late eluting compounds. In addition, the efficiency and selectivity of the Rxi-SVOCms column provided good separation of isobaric PAHs, such as benzo[b]fluoranthene and benzo[k]fluoranthene. Good resolution was also obtained for indeno[123-cd]pyrene and dibenz[ah]anthracene (even when there is a disproportionate response), which minimizes the potential for biased results and reporting false positives.

	Peaks	tR (min)
1.	Naphthalene	6.27
2.	2-Methylnaphthalene	7.09
3.	1-Methylnaphthalene	7.21
4.	Biphenyl	7.66
5.	2,6-Dimethylnaphthalene	7.84
6.	Acenaphthylene	8.17
7.	(IS) Acenaphthene-d10	8.35
8.	Acenaphthene	8.39
9.	2,3,5-Trimethylnaphthalene	8.86
10.	Fluorene	9.02
11.	Dibenzothiophene	10.03
12.	(IS) Phenanthrene-D10	10.16
13.	Phenanthrene	10.19

	Peaks	tR (min)
14.	Anthracene	10.25
15.	1-Methylphenanthrene	10.95
16.	Fluoranthene	11.65
17.	Pyrene	11.92
18.	Benz[a]anthracene	13.46
19.	(IS) Chrysene-D12	13.47
20.	Chrysene	13.51
21.	Benzo[b]fluoranthene*	15.14
22.	Benzo[k]fluoranthene	15.19
23.	(SS) Benzo[a]pyrene-d12	15.66
24.	Benzo[a]pyrene	15.70
25.	Indeno[1,2,3-cd]pyrene	17.78
26.	Dibenz[a,h]anthracene	17.83
27.	Benzo[ghi]perylene	18.27

* Benzo[b]fluoranthene and benzo[j]fluoranthene coelution.

Column	Rxi-SVOCms, 30 m, 0.25 mm ID, 0.25 µm (cat.# 16623)
Standard/Sample	NIST SRM 1597a - complex mixture of polycyclic aromatic hydrocarbons from coal tar
Diluent:	Dichloromethane
Injection
Inj. Vol.:	1 µL split (split ratio 20:1)
Liner:	Topaz 4.0 mm ID single taper inlet liner with wool (cat.# 23303)
Inj. Temp.:	250 °C
Split Vent Flow Rate:	24 mL/min
Oven
Oven Temp.:	40 °C (hold 0.5 min) to 280 °C at 20 °C/min to 330 °C at 6 °C/min (hold 4 min)
Carrier Gas	He, constant flow
Flow Rate:	1.2 mL/min

Detector	MS
Mode:	SIM
SIM Program:
Group Start Time (min) Ion(s) (m/z) Dwell (ms) 1 5.00 127.05, 128.05, 129.00 10 2 6.75 115.10, 139.00, 141.00, 142.05 10 3 7.47 141.00, 152.00, 153.05, 154.05, 155.05, 156.10, 162.10, 164.10 10 4 8.03 150.00, 151.05, 152.05, 153.05, 154.10, 162.10, 164.10 10 5 8.66 153.05, 155.10, 163.05, 164.10, 165.05, 166.05, 169.10, 170.10 10 6 9.62 139.00, 151.95, 176.10, 177.10, 178.10, 179.10, 183.95, 185.00, 188.10, 189.10 10 7 10.71 189.05, 190.05, 191.10, 192.10 10 8 11.37 200.10, 201.10, 202.10, 203.05 10 9 11.81 200.10, 201.05, 202.05, 203.05 10 10 12.84 114.00, 120.00, 226.10, 227.10, 228.10, 229.10, 240.10 10 11 14.44 126.00, 132.00, 250.10, 252.10, 253.10, 264.00 10 12 15.51 126.00, 132.00, 250.05, 252.05, 253.05, 264.00 10 13 16.95 137.95, 139.00, 274.05, 276.10, 277.10, 278.10, 279.10 10 14 18.10 138.00, 274.05, 276.10, 277.10 10
Transfer Line Temp.:	280 °C
Analyzer Type:	Quadrupole
Source Type:	Extractor
Extractor Lens:	6 mm ID
Source Temp.:	330 °C
Quad Temp.:	150 °C
Tune Type:	DFTPP
Ionization Mode:	EI
Instrument	Agilent 7890B GC & 5977A MSD
Sample Preparation	NIST SRM 1597a was diluted 5x in dichloromethane. Isotope-labeled IS/SS are 20 pg on-column. Samples were aliquoted into amber 2 mL, 9 mm short-cap, screw-thread vials (cat.# 21143) containing glass Big Mouth inserts (cat.# 21782) and sealed with 2.0 mL, 9 mm short-cap, screw-vial closures (cat.# 23842).
Notes	The internal standard and surrogate standard mass on column is 20 pg.

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