Andrea Caruso and Massimo Santoro
Thermo Fisher Scientific, Milan, Italy
Appli cat i on N ote 1 0 3 4 2
Automated Determination of Gasoline
Range Organics (GRO) in Water Via
Valve-and-Loop Headspace GC
Key Words
Petroleum, hydrocarbons, water, flame ionization detector, headspace,
EPA Method 5021A, EPA Method 8015D
Goal
The purpose of this application note is to optimize the analytical set-up for
the determination of gasoline range organics in water.
Introduction
Oil spills of varying magnitudes can be a serious source
of contamination of the surrounding environment, in
particular for bodies of water. Water pollution can pose a
serious threat to the affected ecosystem and the encircling
area habitability. For this reason, it is important to have
an accurate and effective system for screening and
evaluating possible contaminations.
Markers of possible water contaminations are gasoline
range organics (GRO) which correspond to the range of
alkanes from C6 to C10 and covering a boiling point range
of approximately 60 °C – 170 °C1. EPA method 5021A2
is applicable to a wide range of organic compounds,
including GRO, that have sufficiently high volatility
to be effectively removed from soil/sediment, solid waste,
aqueous, and water-miscible liquid samples using an
equilibrium headspace procedure.
Similar to EPA method 8015D3, a simple and reliable
GC/FID system could then be used for the quantification
of volatile organics or as a screening technique prior to
headspace GC/MS quantitative analysis.
The headspace analysis can be performed with a
chromatographic system composed of a Thermo
Scientific™ TriPlus™ 300 Headspace autosampler and a
Thermo Scientific™ TRACE™ 1310 GC controlled by
the Thermo Scientific™ Dionex™ Chromeleon™ 7.2
Chromatography Data System (CDS) software. This
system allows sample analysis and data processing to
occur in an automated, reproducible, and reliable manner.
Equipment
A TriPlus 300 Headspace autosampler and the
TRACE 1310 GC are used for the analysis. The data
are collected and processed with Chromeleon 7.2 CDS.
The system is equipped with one Instant Connect
Split/Splitless (SSL) injector with a dedicated headspace
liner (P/N 453A1335) and an Instant Connect Flame
Ionization Detector (FID).
A Thermo Scientific™ TRACE™ TR-1 column was used
with the following dimensions: 30 m × 0.32 mm × 3 µm
(PN 260A395P).
The standards used for calibration are acquired from
Restek™ (PVOC/GRO mix (Wisconsin) PN 30095).
The calibration curves are made with seven levels at the
following concentrations for each analyte: 10 ppb, 50 ppb,
100 ppb, 1 ppm, 5 ppm, 10 ppm, and 100 ppm.
2
Analysis
Results and Discussion
The sample analyzed is 5 mL of water placed into a
20 mL vial. Vials are tightly closed with magnetic caps
(Thermo Scientific™ La-Pha-Pack™ Aluminum Crimp
Seals, PN 18091307). The TriPlus 300 Headspace
sampling system parameters are configured as follows:
Table 1 reports the calibration results for all the
compounds tested. All the calibration curves show
outstanding linearity in the tested range.
• Equilibration time of the sample is 25 min with vial
shaking set to high
Table 1. Calibration results for all compounds.
Number of
Points
Coeff. of
Determination
MTBE
7
0.99999
• Transfer line temperature set to 95 °C
Benzene
7
0.99975
• Pressurization mode is set to Pressure; pressure is set to
1 bar and the pressure equilibration time to 0.2 min
Toluene
7
0.99980
Ethylbenzene
7
0.99986
m-Xylene/p-Xylene
7
0.99989
• Loop size is 1 mL
o-Xylene
7
0.99992
• Injection mode is Standard, and injection time is set to
0.5 min
1,3,5-Trimethylbenzene
7
0.99997
1,2,4-Trimethylbenzene
7
0.99998
Naphthalene
7
0.99987
• Oven temperature set to 85 °C
• Manifold temperature set to 95 °C
• Loop filling mode is set to Pressure; pressure is set to
0.5 bar with an equilibration time of 0.1 min
• Sample line is purged after injection for 1 min at
100 mL/min
• Vial venting is set to On
The TRACE 1310 GC parameters are configured
as follows:
• Starting temperature at 50 °C, hold 1 min, then raise at
15 °C/min up to 220 °C, hold 2 min.
• SSL inlet temperature is set to 150 °C, split mode with
split flow 60 mL/min with a split ratio of 20:1
• Carrier used is helium, with a constant flow of 3 mL/min
• FID temperature is set to 300 °C
Peak Name
MTBE
90
80
70
60
Area
40
215.4
200.0
200.0
187.5
187.5
175.0
175.0
162.5
162.5
150.0
150.0
137.5
137.5
125.0
125.0
112.5
112.5
100.0
100.0
87.5
30
75.0
75.0
62.5
62.5
20
50.0
50.0
37.5
37.5
25.0
25.0
12.5
0
-5.6
12.5
0
-5.6
-11
10
0
-7
-4 0
215.4
20
40
60
Amount
80
100
121
Ethylbenzene
-11
426
0
20
40
60
Amount
80
100
120 128
m-Xylene/p-Xylene
190.2
200.0
400
187.5
375
175.0
350
162.5
325
150.0
300
137.5
137.5
275
125.0
125.0
250
112.5
225
100.0
Area
112.5
100.0
12.5
0
-5.6
-11
0
20
40
60
Amount
80
100
120 128
1,3,5-Trimethylbenzene
190.2
25.0
12.5
-19
0
20
40
60
Amount
80
100
120 134
1,2,4-Trimethylbenzene
0
-8.7
-37 -20
68.5
65.0
150.0
55.0
137.5
137.5
50.0
125.0
125.0
45.0
112.5
112.5
40.0
100.0
100.0
35.0
87.5
75.0
75.0
62.5
62.5
50.0
50.0
37.5
37.5
25.0
25.0
12.5
12.5
0
-8.7
-37 -20
0
-8.7
-37 -20
40
60
80
Amount
100
120
140 150
Figure 1. Calibration curves of some of the target analytes.
0
20
40
60
80
Amount
100
120 140 150
Naphthalene
60.0
Area
Area
162.5
150.0
Area
175.0
20
o-Xylene
37.5
162.5
0
120128
87.5
175.0
87.5
100
50.0
25
0
-16
80
62.5
50
25.0
60
Amount
75.0
75
37.5
190.2
200
100
50.0
40
150.0
125
62.5
20
162.5
150
75.0
0
175.0
175
87.5
3
Toluene
87.5
Area
Area
50
Area
Benzene
215.4
Area
100
30.0
25.0
20.0
15.0
10.0
5.0
0
0
20
40
60
80
Amount
100
120
140 150
-4.8
-68 -50
0
50
Amount
100
150
184
4
100
90
80
m-Xylene/p-Xylene
70
60
50
Ethylbenzene
o-Xylene
40
pA
30
20
10
0
-10
-20
-30
-42
7
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9
8
Minutes
Figure 2. Separation of the couple ethylbenzene m/p-xylene at a resolution of 1.83.
Table 2. Repeatability results of each GRO compound at 1 ppm in water. Peak Area is expressed in pA*sec.
MTBE
Benzene Toluene Ethylbenzene m/p-Xylene o-Xylene 1,3,5-Trimethylbenzene 1,2,4-Trimethylbenzene Naphthalene
1
57.3628 55.8949 59.9575
59.6926
126.4131
74.4254
66.2386
77.0404
56.238
2
57.0797 55.4711 59.4999
59.3961
125.7007
74.0777
65.9278
76.7329
56.1561
3
57.5383 56.4514 60.8489
60.9327
128.8599
75.7043
67.8679
78.6368
56.355
4
57.6155 56.1589 60.3285
60.3256
127.5803
75.0778
67.0354
77.8603
56.5539
5
57.102
59.9814
126.7492
74.5956
66.5793
77.2604
55.9639
6
57.4345 56.2741 60.466
60.4806
127.7841
75.1562
67.2012
77.7268
56.0468
7
58.2604
57.1632 61.5558
61.641
130.1047
76.5622
68.5266
79.4365
56.7669
8
58.7969
57.4769 61.8347
61.8393
130.5417
76.8693
68.6879
79.5756
57.3098
9
57.3306
57.3574 61.3496
61.0969
128.8684
75.6615
67.4593
78.0111
55.9104
55.7743 59.9651
Standard
Deviation
0.5641
0.7267
0.8032
0.8457
1.6559
0.9457
0.9607
1.0069
0.4498
Relative
Standard
Deviation
0.98%
1.29%
1.32%
1.40%
1.29%
1.26%
1.43%
1.29%
0.80%
Figure 2 shows good separation of the couple ethylbenzene m/p-xylene, whose resolution is 1.83.
Repeatability has been evaluated for each compound and the results are reported in Table 2.
5
100
90
80
m-Xylene/p-Xylene
70
1,3,5-Trimethylbenzene
Ethylbenzene
60
o-Xylene
50
pA
1,2,4-Trimethylbenzene
Toluene
Benzene
40
Naphthalene
30
MTBE
20
10
0
-10
0
1
2
3
4
5
6
Minutes
7
8
9
10
11
12
12.5
Figure 3. PVOC/GRO mix (Wisconsin) standard in water at 1 ppm.
11
10.5
10
9.5
9
8.5
pA
Toluene
8
1,3,5-Trimethylbenzene
7.5
m-Xylene/p-Xylene
MTBE
7
6.5
o-Xylene
6
Naphthalene
1,2,4-Trimethylbenzene
Ethylbenzene
Benzene
5.5
5
4.5
4
0
1
2
3
4
5
6
7
8
9
10
11
12
12.5
Minutes
Figure 4. Chromatogram of tap water spiked with gasoline.
Blank samples have been analyzed after each sequence of at least 10 samples, and they showed a clear baseline.
Figure 3 shows a chromatogram of the Wisconsin standard mix at the 1 ppm calibration point, and Figure 4 shows
the chromatogram of a tap water sample spiked with gasoline.
References
As the results confirm, the system comprised of the
TriPlus 300 Headspace autosampler, the TRACE 1310
GC, and Chromeleon CDS is a reliable and automated
solution for Gasoline Range Organics in water. With its
120-vial sample tray and the large 18-vial incubation
oven overlap capacity, the system guarantees excellent
throughput. The inertness of the entire sample path and
high temperature capability eliminate any carryover
effect, ensuring the highest sample integrity and results
consistency. The optional barcode capabilities of the
autosampler and the accurate auditing capabilities of
Chromeleon CDS also ensure the highest data quality
and traceability.
1. “Interlaboratory Study of Three Methods for
Analyzing Petroleum Hydrocarbons in Soils,” API.
Publication Number 4599, American Petroleum
Institute, March 1994.
2. EPA Method 5021A.
3. EPA Method 8015D.
www.thermofisher.com
©2016 Thermo Fisher Scientific Inc. All rights reserved. Restek is a trademark of Restek Corp. All other trademarks are the property
of Thermo Fisher Scientific Inc. and its subsidiaries. This information is presented as an example of the capabilities of Thermo Fisher
Scientific Inc. products. It is not intended to encourage use of these products in any manners that might infringe the intellectual property
rights of others. Specifications, terms and pricing are subject to change. Not all products are available in all countries. Please consult your
local sales representative for details.
Africa-Other +27 11 570 1840
Australia +61 3 9757 4300
Austria +43 810 282 206
Belgium +32 53 73 42 41
Canada +1 800 530 8447
China +86 10 8419 3588
Denmark +45 70 23 62 60
Europe-Other +43 1 333 50 34 0
Finland +358 9 3291 0200
France +33 1 60 92 48 00
Germany +49 6103 408 1014
India +91 22 6742 9494
Italy +39 02 950 591
Japan +81 45 453 9100
Latin America +1 561 688 8700
Middle East +43 1 333 50 34 0
Netherlands +31 76 579 55 55
New Zealand +64 9 980 6700
Norway +46 8 556 468 00
Russia/CIS +43 1 333 50 34 0
South Africa +27 11 570 1840
Spain +34 914 845 965
Sweden +46 8 556 468 00
Switzerland +41 61 716 77 00
UK +44 1442 233555
USA +1 800 532 4752
AN10342_E 08/16S
Appli cat i on N ote 1 0 3 4 2
Conclusion