Detection of Sulfur Compounds in
Natural Gas According to ASTM
D5504 with an Agilent Dual Plasma
Sulfur Chemiluminescence Detector

Application NoteAuthor

Abstract

Rebecca Veeneman

Sulfur compounds in natural gas samples are detected using an Agilent 7890B
gas chromatograph conﬁgured with an Agilent 8355 dual plasma sulfur
chemiluminescence detector (SCD). The 8355 SCD provides linear, equimolar
responses from 0.15 to 10 ppm.

Introduction

Experimental

The petrochemical industry’s proﬁts
are generated by keeping their cleanup,
reﬁning, blending, and characterization
processes running as efﬁciently aspossible. Most of these processes canbe negatively impacted when dealing
with sulfur compounds. Being able tomeasure sulfur compounds reliably androutinely is an absolute must so that they
can optimize their processes at any giventime.

An Agilent 7890B GC was conﬁgured
with a deactivated two-valve system,
and an Agilent 8355 SCD. Sample
introduction was achieved through a
10-port gas sample valve interfaced toa deactivated purged ultimate union
through deactivated tubing. Standards

When dealing with natural and petroleum
gases, sulfur compounds can be present
in two forms. First, naturally occurring
contaminates during harvest. Secondly,
sulfur-based odorant additives fortraceability and safety purposes.
A gas chromatograph (GC) equipped witha sulfur chemiluminescence detector(SCD) provides a rapid and efﬁcientmeans of identifying and quantifying thesulfur compounds present at the various
reﬁnement stages. Various detectors exist
for the detection of sulfur compounds,
but the SCD provides the most speciﬁcand sensitive method for analysis.
ASTM D5504 provides guidelines for thedetermination of volatile sulfur-containing
compounds in high methane content
gaseous fuels. It has been successfully
applied to other fuel-type gases
containing sulfur compounds thatare often regulated and monitored byregulatory commissions as well as theproduction/distribution facilities.
The Agilent 8355 dual plasma SCD
provides linear, equimolar responses
to sulfur-containing compounds withminimal hydrocarbon interference. This
improves ease-of-use for data collection
and analysis since it eliminates the needto linearize the data, and determine
separate response factors for eachcompound of interest. The 8355 SCD
also provides a stable response thatis not quenched by hydrocarbons.
This Application Note addresses thelinearity, stability, and practical detection
limits of the 8355 SCD installed onan Agilent 7890B GC equipped with aDB-Sulfur SCD column of 4.3 µm ﬁlm
thickness.

were diluted using an online dilutor
that interfaced through a 6-port gas
sample valve. Figure 1 shows the valve
conﬁguration used. Table 1 presents
the compound information. The sulfur
standards were blended with helium forthis application, but the system is capableof introducing matrix.
Column/SCD
Sample 2 (matrix) in

Carrier gas

50 µL sample loop
50 µL sample loop

Sample 1 out

Sample 2 (matrix) out
Purge out
Purge inSample 1 inVent

Diluted standard
Vent

Figure 1. A diagram of the 2-valve system used for dilution and sample introduction is shown.
Table 1. Sulfur standards components.
CompoundFormulaHydrogen sulﬁde

H2S

Carbonyl sulﬁde

COS

Methyl mercaptan

CH3SH

Ethyl mercaptan

CH4CH3SH

Dimethyl sulﬁdeCH3SCH3

Carbon disulﬁdeCS22-Propanethiol

CH3SCH2H5

tert-Butyl mercaptan(CH3)3CSH

1-propanethiol

CH3(CH2)2SH

Thiophene

C4H4S

n-Butyl mercaptan

CH3(CH2)3SH

Diethyl sulﬁdeCH3CH2SCH2CH3

Methyl ethyl sulﬁdeCH3SCH2CH3

2-Methyl-1-propanethiol(CH3)2CHCH2SH

1-Methyl-1-propanethiol

CH3CH2CHSHCH32

Table 2 shows instrument conditions.

Results and Discussion

Table 2. Instrument conditions.
Parameter

Value

Agilent 7890B GC

Repeatability and linearity

Sample introduction

10-port GSVLinearity was evaluated for the15 analytes ranging from approximately0.1 to 10 ppm. Table 3 gives therepeatability (calculated as the peak area
RSD of 10 injections) for each analyte
at each concentration, along with R2values. The two lowest concentrations
gave the highest average RSD, at
6.3 %. Concentrations in the 5.5 ppm
and 1.5 ppm yielded better average
RSDs of 2.0 % and 2.7 %, respectively.
Analytes such as 1-propanethiol yieldedhigher area RSDs, in general due tothe decreased resolution between itand thiophene. Later-eluting analytes
also showed higher RSDs due to lowresponses. The highest concentration at
9.9 ppm yielded an average RSD of 5.0 %.
The linearity was generally good, with anaverage R2 value of 0.996.

Temperature

150 °COven

30 °C (1.5 minutes) 15 °C to 250 °C (3 minutes)

ColumnAgilent DB-Sulfur SCD, 70 m × 530 µm, 4.3 µm (G3903-63003)

Constant ﬂow

6 mL/minAgilent 8355 SCD
Base temperature

250 °C

Burner temperature

800 °C

Upper H2 ﬂow

38 mL/min

Lower H2 ﬂow

8 mL/minOxidizer ﬂow

60 mL/min

Ozone generator

40 mL/min

Nominal burner pressure

366 torr

Nominal reaction cell vacuum

3–5 torrTable 3. Repeatability and linearity for the 15 sulfur compounds analyzed.
Analyte9.9 ppm

5.5 ppm

1.5 ppm

0.793 ppm 0.149 ppm

R2

Hydrogen sulﬁde

4.4 %

1.0 %

0.7 %

5.8 %

6.7 %

0.999

Carbonyl sulﬁde

2.3 %

0.4 %

2.4 %

6.0 %

6.5 %

0.9996

Methyl mercaptan

4.6 %

0.9 %

1.7 %

6.4 %

10 %

0.99790.9982Ethyl mercaptan

5.3 %

1.0 %

1.6 %

5.4 %

ND

Dimethyl sulﬁde

4.0 %

0.6 %

1.1 %

4.0 %

9.0 %

0.9997

Carbon disulﬁde

4.2 %

0.8 %

0.6 %

4.2 %

4.3 %

0.99992-propanethiol

5.8 %

4.3 %

4.9 %

9.4 %

ND

0.9753tert-Butyl mercaptan

5.7 %

1.3 %

3.3 %

6.6 %

ND

0.99761-Propanethiol

9.0 %

5.5 %

4.7 %

ND

ND

0.9934

Thiophene

4.6 %

1.2 %

1.8 %

4.8 %

3.5 %

0.9999n-Butyl mercaptan

4.8 %

0.9 %

1.4 %

3.5 %

4.8 %

0.99980.9833

Diethyl sulﬁde

6.1 %

5.5 %NDND

ND

Methyl ethyl sulﬁde

5.4 %

1.4 %

2.3 %

8.9 %

ND

0.9986

2-Methyl-1-propanethiol

3.9 %

2.6 %

7.6 %

7.8 %

ND

0.9979

1-Methyl-1-propanethiol

5.3 %

2.4 %

3.5 %

9.4 %

ND

0.99903Linearity was very good for all thecompounds evaluated. Figure 2 shows
calibration plots for four analytes ofinterest. The four analytes chosen arerepresentative of the 15 compounds
evaluated, and demonstrate thelinearity observed across the various
functional groups and retention times.
Five replicate injections were plotted ateach concentration level, demonstratingsuperior conﬁdence of repeatability
across the concentration range.

Carbon disulﬁde (RT = 6.80 min)
25,00025,00020,000

Average peak area

Average peak area

Hydrogen sulﬁde (RT = 3.45 min)
30,00020,00015,00010,00015,00010,0005,000
002

468Concentration (ppm)

10

5,000
0120

Thiophene (RT = 7.95 min)Average peak area

Average peak area

10,000
8,000
6,000
4,000
2,000
02468
Concentration (ppm)

468Concentraion (ppm)10121-Methyl-1-propanethiol (RT = 11.57 min)12,000021012900
800700600
500
400300200
100002468Concentration (ppm)

Figure 2. Calibration plots for four sulfur compounds of interest. These plots are representative of the 15 analytes examined.

41012Limit of detection (LOD) evaluation

Table 4. A practical LOD was determined for the 15 component mix from the 1.5 ppm standard.

Using the standard at approximately
1.5 ppm, a practical LOD was calculatedfor each compound in the mix. Table 4shows that the detection limits rangefrom 0.076 pg/sec for hydrogen sulﬁde to
5.548 pg/sec for 1-propanethiol. Diethyl
sulﬁde was not detected at the 1.5 ppm
concentration because of its coelution
with methyl ethyl sulﬁde. Analytes
with less resolution (for example,1-propanethiol and diethyl sulﬁde) show
higher LODs. As with repeatability, thelater-eluting compounds also show higher
LODs because of their low responses.
Figure 3A shows a representative
chromatogram from the 1.5 ppm
standard used in this determination ofdetection limits. Figure 3B shows thechromatogram obtained from the 150 ppb
concentration for comparison.

PeakAnalyte

LOD (pg/sec)

1

Hydrogen sulﬁde

0.076

2

Carbonyl sulﬁde

0.18

3

Methyl mercaptan

0.45

4

Ethyl mercaptan

1.05

Dimethyl sulﬁde

0.19

6

Carbon disulﬁde

0.090

72-Propanethiol

1.4

8

tert-Butyl mercaptan

1.691-Propanethiol

6.2

10

Thiophene

0.21

11n-butyl mercaptan

0.22

12

Diethyl sulﬁdeND

13

Methyl ethyl sulﬁde

0.39

142-Methyl-1-propanethiol

3.215

1-Methyl-1-propanethiol

2.4pA

12,0001,500
61,00025500

37890024111046Time (min)1281314151012Figure 3A. The sulfur standard at 1.5 ppm. This concentration was used calculate LODs for this mix.
pA

6120
2100
80

11160
5340024476Time (min)898101213 1410Figure 3B. The sulfur standard at 150 ppb. While some analytes are not detected, hydrogen sulﬁde (1), carbonyl sulﬁde (2),carbon disulﬁde (6), and n-butyl mercaptan (11) show excellent peak shape.

51512Conclusions

ReferenceThe petrochemical industry relies
heavily on measuring sulfur compounds
throughout their various processes.
Sulfur compounds naturally exist, or areadded to natural gas and liquid petroleum
gases. The quantitation of such gases isnecessary for quality control and safety
purposes.

1. ASTM D5504-98: Standard test
method for determination of sulfur
compounds in natural gas andgaseous fuels by gas chromatography
and chemiluminescence.

The Agilent 8355 dual plasma sulfur
chemiluminescence detector provides
a linear response for a wide range ofsulfur-containing compounds. Arearepeatability is very good for most theanalytes examined down to 150 ppb.
Linearity was very good for all analytes
in the standard, with a practical LOD
of 0.5 pg/sec or better for over half ofthe compounds. While this is ﬂow rate
and analyte dependent, it is roughly
equivalent to 500 ppb, which is more thanadequate for many ASTM applications.

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This information is subject to change without notice.
© Agilent Technologies, Inc., 2016
Published in the USA, April 4, 2016
5991-6819EN