Detection of Sulfur Compounds According
to ASTM D5623 in Gasoline with Agilent's
Dual Plasma Sulfur Chemiluminescence
Detector (G6603A) and an Agilent 7890A
Gas Chromatograph
Application
Hydrocarbon Processing
Authors
Wenmin Liu
Agilent Technologies Co. Ltd.
412 Ying Lun Road
Waigaoqiao Free Trade Zone
Shanghai, 200131
China
Mario Morales
Agilent Technologies, Inc.
2850 Centerville Road
Wilmington, DE 19808
USA
Abstract
Sulfur components in gasoline samples are detected utilizing ASTM D 5623 with an Agilent 7890A GC configured
with Agilent 355 dual plasma sulfur chemiluminescence
detector (DP SCD). The 355 SCD response is linear,
equimolar, and provides a linear range from 0.1 to 10 ppm.
The coelution of hydrocarbon and sulfur peaks does not
present a problem for the detector. The detection limits of
sulfur compounds in gasoline are down to 20 ppb, while
no quenching was found in the gasoline sample analysis.
Introduction
Gas chromatography with sulfur chemiluminescence detection (SCD) provides a rapid and highly
specific means to identify and quantify various
sulfur compounds that may be present in petroleum feed stocks and products, such as gasoline.
Frequently, petroleum feeds and products contain
varying amounts and types of sulfur compounds.
Many sulfur compounds can be corrosive to equipment, can inhibit or destroy catalysts employed in
downstream processing, and can impart undesirable odors to products. The ability to speciate
sulfur compounds in various petroleum liquids is
useful in controlling sulfur compounds in finished
products and is frequently more important than
the ability to simply measure total sulfur content
alone.
The SCD burner easily mounts on the 6890 and
7890A GCs, and incorporates features for easier
and less frequent maintenance. The DP technology
harnesses the power of dual flame plasma combustion, optimizing combustion of the sample matrix
and formation of sulfur monoxide (SO).
The 355 DP SCD response is inherently linear,
equimolar, and far less susceptible to hydrocarbon
interference. These advantages eliminate the need
for linearizing data or determining separate
response factors for individual sulfur compounds.
Furthermore, hydrocarbons are virtually invisible
to the DP SCD. The coelution of hydrocarbon and
sulfur peaks does not show quenching. Frequent
column changes are required for analysis of various hydrocarbon products by flame photometric
detectors (FPD) to avoid serious quenching and
inaccurate results. ASTM Method D5623 utilizes
the sulfur chemiluminescence detector (SCD) for
the detection of sulfur compounds in gasoline.
Experimental
Experimental Conditions
An Agilent 7890A GC configured with split/splitless inlet (Sulfinert-treated), 7683B autosampler,
and Agilent 355 DP SCD were used. The sulfur
standards in toluene and iso-octane (10:90) were
purchased from Supelco (Bellefonte, PA). The component information is in Table 1.
7890A GC Conditions
Table 1.
Sulfur Standards Components
Concentration
(ppm) (w/w)
Components
Formula
1 Ethyl mercaptan
CH3CH3SH
11.62
2 Dimethyl sulfide
(CH3)2S
11.92
3 Carbon disulfide
C2S
17.84
4 Isopropyl mercaptan
(CH3)2CHSH
34.32
5 T-butyl mercaptan
(CH3)3CSH
11.28
6 n-propyl mercaptan
CH3CH2CH2SH
7 Methylethyl sulfide
CH3CH2SCH3
11.87
8 Thiophene
C4H4S
14.81
5.93
9 Sec-butyl mercaptan
CH3CH2CH(SH)CH3
10 n-butyl mercaptan
CH3(CH2)3SH
11 Dimethyl disulfide
CH3SSCH3
14.75
12 2-methyl thiophene
C5H6S
14.29
13 3-metyl thiophene
C5H6S
21.35
14 Diethyl disulfide
(C2H5)2S2
27.99
15 Benzo(b)thiophene
C8H6S
40.49
23.26
5.89
NIST Standard Reference Material 2299, Sulfur in
Gasoline, was used. The total sulfur in gasoline is
13.6 ± 1.5 µg/g based on analyses by isotope dilution thermal ionization mass spectrometry (IDTIMS). Homogeneity testing was performed using
X-ray fluorescence spectrometry.
2
Front inlet
Split/splitless (Sulfinert-treated
capillary inlet system)
Heater
275 °C
Pressure
10.951 psi
Septum purge flow
3 mL/min
Mode
Split
Gas saver
20 mL/min after 2 min
Split ratio
10 :1
Split flow
15 mL/min
Oven
30 °C (1 min) 10 °C/min 250 °C (1 min)
Column
HP-1 30 m × 0.32 mm × 4 µm
(P/N 19091Z-613)
SCD Conditions – Agilent G6603A
Burner temperature
800 °C
Vacuum of burner
372 torr
Vacuum of reaction cell
5 torr
H2
40 mL/min
Air
53 mL/min
Results and Discussion
Several commercially available sulfur detectors are
available for the determination of sulfur compounds in various matrices. When compared to
flame photometric detection (FPD), pulsed flame
photometric detection (PFPD), atomic emission
detection (AED), and inductively coupled plasmamass spectrometry (ICP-MS), the SCD shows the
best performance based on stability, cost, and
quantification. [2,3]
With DP technology, the performance of Agilent
355 SCD has been further enhanced, for unsurpassed stability, selectivity, and lack of quenching.
Table 2 lists the DP SCD stability at different sulfur
levels.
Table 2.
Repeatability of Sulfur Compounds at Different Concentrations (Refer to Table 1 for peak identification.)
Con. ppm
1
1.16
2
1.79
3
1.78
4
3.42
5
1.13
6
0.59
7
1.19
8
3.80
10
0.59
RSD (%)
2.8
3.6
3.1
1.9
3.0
2.7
3.9
3.9
2.9
2.1
2.2
2.9
0.4
3.7
Con. ppm
0.12
0.18
0.18
0.34
0.11
0.06
0.12
0.38
0.06
0.15
0.14
0.21
0.28
0.4
RSD (%)
5.7
7.4
3.4
3.7
6.6
4.8
5.7
4.8
8.0
4.0
3.3
4.7
7.3
3.1
Correlation coefficients of the tested sulfurs over
three orders of magnitude were better than 0.99
(R2). Table 3 shows the linearity of each sulfur
Table 3.
compound. Figure 1 shows the chromatogram of
sulfurs in a hydrocarbon matrix without interference (1 to approximately 2 µg/kg).
Linear Ranges of Tested Sulfurs (Refer to Table 1 for
peak identification.)
Analytes
0.1ppm to 10ppm
0.9975
2
0.1ppm to 10ppm
0.9982
15
14
13
3500
3000
12
7
2500
1
11
8/9
34
Linearity (R2)
Concentration Range
11
12
13
14
15
1.47 1.43 2.14
2.80 4.0
12
2000
5
6
1500
10
1000
3
0.1ppm to 10ppm
0.9991
4
0.1ppm to 10ppm
0.9992
5
0.1ppm to 10ppm
0.9995
6
0.1ppm to 10ppm
0.9996
7
0.1ppm to 10ppm
0.9998
8/9
0.1ppm to 10ppm
0.9998
10
0.1ppm to 10ppm
0.9994
11
0.1ppm to 10ppm
0.9999
12
0.1ppm to 10ppm
0.9997
13
0.1ppm to 10ppm
0.9995
14
0.1ppm to 10ppm
0.9997
15
0.1ppm to 10ppm
0.9999
Table 4.
500
0
2.5
Figure 1.
5
7.5
10
12.5
15
17.5
20
m in
Chromatogram of sulfur standard in hydrocarbon
matrix. (Refer to Table 1 for peak identification.)
The data in Table 4 illustrate the sensitivity (S/N)
of 355 SCD for trace-level analysis (approximately
20 ng/kg) of sulfurs in a hydrocarbon matrix.
Figure 2 shows the chromatogram of trace sulfurs,
which also indicates no interferences in the analysis.
Sulfur Sensitivity (Refer to Table 1 for peak identification.)
Peak No.
1
2
3
4
5
6
7
8/9
S/N
2.0
2.5
5.0
4.6
1.8
1.6
2.4
5.0
10
1.5
11
3.6
12
2.0
13
4.6
14
3.2
15
5.2
15µV
1000
800
600
15
400
200
1 2
3
4
5 67
8/9
10
11 1213
14
0
Figure 2.
Chromatogram of sulfurs at trace levels (20 ng/g).
(Refer to Table 1 for peak identification.)
3
www.agilent.com/chem
Gasoline Samples Analysis
Conclusions
NIST Standard Reference Material 2299 was
detected on an Agilent SCD and the mass concentration of total sulfur in sample was calculated by
summing the sulfur content of all sulfur components (known and unknown) in the sample to
arrive at its total sulfur value as recommended by
ASTM 5623.
The Agilent DP SCD is used for the detection of
sulfur compounds in a complex hydrocarbon
matrix. The results show that the DP SCD has
linear response to sulfur compounds without
quenching, yielding MDLs down to 20 ng/g. This
solution is available as an Agilent preconfigured
system; please refer to Agilent SP1 7890-0365 for
ordering information.
Figure 3A shows the chromatogram of the sulfur
standard and Figure 3B shows the chromatogram
of the standard gasoline sample. The total amount
of sulfur is calculated by summing all the peak
areas in Figure 3B and quantitated as thiophene
11.8 µg/g of total sulfur with an RSD 2.7% (n = 5)
was calculated in the gasoline sample. This was
within the specified range of 13.6 ± 1.5 µg/g.
14
15µV
4
1000
8/9
3
15
11
800
13
600
12
7
400
12
56
10
200
0
0
2
4
6
8
10
12
14
16
18
min
References
1. ASTM 5623: Standard test method for sulfur
compounds in light petroleum liquids by gas
chromatography and sulfur selective detection
2. Roger L. Firor and Bruce D. Quimby, “Analysis
of Trace Sulfur Compounds in Beverage-Grade
Carbon Dioxide,” Agilent Technologies publication 5988-2464EN
3. Roger L. Firor and Bruce D. Quimby, “A Comparison of Sulfur Selective Detectors for LowLevel Analysis in Gaseous Streams,” Agilent
Technologies publication 5988-2426EN
For More Information
Figure 3A. Chromatogram of sulfur standard.
For more information on our products and services,
visit our Web site at www.agilent.com/chem.
8/9
15µV
1000
2
800
11
600
7
3
14
12
400
4
200
13
6
5
0
0
2
4
6
8
10
12
14
16
18
min
Figure 3B. Chromatogram of gasoline standard sample. (Refer
to Table 1 for peak identification.)
Agilent shall not be liable for errors contained herein or for incidental or consequential
damages in connection with the furnishing, performance, or use of this
material.
Information, descriptions, and specifications in this publication are subject to change
without notice.
© Agilent Technologies, Inc. 2008
Printed in the USA
August 12, 2008
5989-9233EN