EN ISO 19739:2005

Natural gas - Determination of sulfur compounds using gas chromatography (ISO 19739:2004)

ISO 19739:2004 specifies the determination of hydrogen sulfide, carbonyl sulfide, C1 to C4 thiols, sulfides and tetrahydrothiophene (THT) using gas chromatography (GC). Depending on the method chosen from those given in its annexes, the application ranges for the determination of sulfur compounds can vary, but whichever of the methods is used, its requirements apply.

Erdgas - Bestimmung von Schwefelverbindungen mittels Gaschromatographie (ISO 19739:2004)

Diese Internationale Norm legt die Bestimmung von Schwefelwasserstoff, Kohlenstoffoxidsulfid, Thiole mit C1 bis C4, Sulfide und Tetrahydrothiopen (THT) mittels Gaschromatographie (GC) fest. Abhängig vom aus den Anhängen gewählten Verfahren kann der Bereich der Anwendbarkeit der Schwefelbestimmung variieren. In jedem Fall gelten bei jedem gewählten Verfahren die Anforderungen dieses Internationalen Standards.

Gaz naturel - Détermination des composés soufrés par chromatographie en phase gazeuse (ISO 19739:2004)

L'ISO 19739:2005 spécifie la détermination du sulfure d'hydrogène, du sulfure de carbonyle, des thiols, C1 à C4, des sulfures et du tétrahydrothiophène (THT) en utilisant la chromatographie en phase gazeuse (CPG). En fonction de la méthode choisie parmi celles données dans les annexes, les plages d'application pour la détermination des composés soufrés peuvent varier, mais quelle que soit la méthode employée, les exigences de la présente Norme internationale s'appliquent.

Zemeljski plin – Določevanje žveplovih spojin s plinsko kromatografijo (ISO 19739:2004)

General Information

• Status: Published
• Publication Date: 15-Nov-2005
• Withdrawal Date: 30-May-2006
• ICS: 75.060 - Natural gas
• Technical Committee: CEN/TC 238 - Test gases, test pressures and categories of appliances
• Drafting Committee: CEN/SS N21 - Gaseous fuels and combustible gas
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 16-Nov-2005
• Completion Date: 16-Nov-2005
• Ref Project: SIST EN ISO 19739:2006 - Natural gas - Determination of sulfur compounds using gas chromatography (ISO 19739:2004)

Relations

• Corrected By: EN ISO 19739:2005/AC:2009 - Natural gas - Determination of sulfur compounds using gas chromatography (ISO 19739:2004/Cor 1:2009)
• Effective Date: 23-Mar-2009

Overview

EN ISO 19739:2005 (ISO 19739:2004) specifies standardized procedures for the determination of sulfur compounds in natural gas using gas chromatography (GC). The standard covers identification and quantification of key sulfur species including hydrogen sulfide (H2S), carbonyl sulfide (COS), C1–C4 thiols (alkane thiols/mercaptans), alkyl sulfides/disulfides and tetrahydrothiophene (THT). Multiple GC-based methods are provided in informative annexes; whichever method is chosen, the general requirements of the standard apply.

Key topics and technical requirements

• Analytes covered: H2S, COS, thiols (mercaptans), sulfides, disulfides, THT and other common natural gas sulfur compounds.
• Analytical principle: Physical separation by GC followed by measurement versus calibrated reference gases; calibration gas and sample must be analyzed under identical conditions.
• Apparatus and columns: Use GC systems with injection, oven temperature and pressure control; column materials and stationary phases must be inert to sulfur and provide chromatographic resolution of at least 1.5 between adjacent peaks.
• Detectors and methods (annexes): Multiple detectors/methods are described (examples in annexes): flame photometric detector (FPD), sulfur chemiluminescence detector (SCD), pulsed flame photometric detector (PFPD), mass spectrometry (MSD), atomic emission detector (AED), electron capture/other detectors (ED), and column-switching approaches - allowing selection to match sensitivity and selectivity needs.
• Sampling and safety: Guidance on sampling practice, temperature and pressure control, materials, purge and flow control; includes a safety warning that some sulfur compounds are hazardous.
• Calibration and traceability: Requirements for calibration using primary/secondary/working reference gas mixtures and references to ISO documents on gas mixture certification and comparison.
• Performance characteristics & reporting: Specifies required performance characteristics for sulfur analyses and test-report content.

Applications and users

• Utilities and pipeline operators monitoring odorants and residual sulfur in distribution/transmission systems.
• Natural gas producers and processing plants (quality control and treatment validation).
• Analytical laboratories performing regulatory compliance, process control, or environmental monitoring.
• Manufacturers of GC equipment and detectors aligning test methods with industry standards.
• Regulators and standards bodies specifying measurement requirements for safety and billing specifications.

Related standards

Normative references cited by ISO 19739 include:

• ISO 5725-2 (accuracy / repeatability)
• ISO 6141, ISO 6143, ISO 6145-10 (calibration gases / preparation)
• ISO 10715 (natural gas sampling)
• ISO 14532 (natural gas vocabulary)

Keywords: EN ISO 19739:2005, ISO 19739, natural gas, sulfur compounds, gas chromatography, hydrogen sulfide, thiols, sulfides, THT, GC detectors, calibration gas, sampling.

Standards Content (Sample)

SLOVENSKI STANDARD
01-februar-2006
=HPHOMVNLSOLQ±'RORþHYDQMHåYHSORYLKVSRMLQVSOLQVNRNURPDWRJUDILMR,62

Natural gas - Determination of sulfur compounds using gas chromatography (ISO
19739:2004)
Erdgas - Bestimmung von Schwefelverbindungen mittels Gaschromatographie (ISO
19739:2004)
Gaz naturel - Détermination des composés soufrés par chromatographie en phase
gazeuse (ISO 19739:2004)
Ta slovenski standard je istoveten z: EN ISO 19739:2005
ICS:
75.060 Zemeljski plin Natural gas
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 19739
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2005
ICS 75.060
English Version
Natural gas - Determination of sulfur compounds using gas
chromatography (ISO 19739:2004)
Gaz naturel - Détermination des composés soufrés par Erdgas - Bestimmung von Schwefelverbindungen mittels
chromatographie en phase gazeuse (ISO 19739:2004) Gaschromatographie (ISO 19739:2004)
This European Standard was approved by CEN on 3 November 2005.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Central Secretariat or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 19739:2005: E
worldwide for CEN national Members.

Foreword
The text of ISO 19739:2004 has been prepared by Technical Committee ISO/TC 193 "Natural
gas” of the International Organization for Standardization (ISO) and has been taken over as EN
ISO 19739:2005 by CMC.
This European Standard shall be given the status of a national standard, either by publication of
an identical text or by endorsement, at the latest by May 2006, and conflicting national standards
shall be withdrawn at the latest by May 2006.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary,
Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

Endorsement notice
The text of ISO 19739:2004 has been approved by CEN as EN ISO 19739:2005 without any
modifications.
INTERNATIONAL ISO
STANDARD 19739
First edition
2004-05-01
Corrected version
2005-11-15
Natural gas — Determination of sulfur
compounds using gas chromatography
Gaz naturel — Détermination des composés soufrés par
chromatographie en phase gazeuse

Reference number
ISO 19739:2004(E)
©
ISO 2004
ISO 19739:2004(E)
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ii © ISO 2004 – All rights reserved

ISO 19739:2004(E)
Contents Page
Foreword. iv
Introduction . iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Principle. 3
5 Apparatus . 3
6 Sampling. 4
6.1 Safety precautions. 4
6.2 Temperature control. 4
6.3 Construction materials. 5
6.4 Cleanness . 5
6.5 Installation of the calibration gas cylinder. 5
6.6 Pressure control . 5
6.7 Purging of reduction valve and transfer lines .5
6.8 Flow control. 6
6.9 Diffusion control . 6
6.10 Automation and sequences of sampling . 6
7 Calibration . 6
8 Analysis . 6
9 Performance characteristics required for sulfur analysis. 7
10 Test report . 8
Annex A (informative) Columns mostly used in sulfur analysis (with internal phase and
dimensions). 9
Annex B (informative) Types of detectors used in sulfur analysis . 10
Annex C (informative) GC method using capillary column and FPD. 13
Annex D (informative) GC method using ED . 19
Annex E (informative) GC method using MSD . 25
Annex F (informative) GC method using AED. 28
Annex G (informative) GC methods using column switching and FPD. 31
Annex H (informative) GC method using capillary column and SCD . 43
Annex I (informative) GC method using capillary column and PFPD . 50
Bibliography . 55

ISO 19739:2004(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 19739 was prepared by Technical Committee ISO/TC 193, Natural gas, Subcommittee SC 1, Analysis of
natural gas.
This first edition of ISO 19739 cancels and replaces ISO 6326-2:1981 and ISO 6326-4:1994, of which it
constitutes a technical revision.
This corrected version of ISO 19739:2004 incorporates the following corrections:
 page 2, 3.2: a prime has been added to the second R in the formula and the description in parenthesis;
 page 2, 3.3: a prime has been added to the second R in the formula and the description in parenthesis;
 page 7, 9 b): the name of the molecule has been corrected to 2-methylpropane-2-thiol;
 pages 20, 31, 43 and 44: the footnotes have been corrected to read ".this International Standard.";
 page 22, D.3.4.2: the temperature has been changed to 293 K;
 page 43: the name of the molecule has been corrected to 2-methylpropane-2-thiol;
 other minor editorial rectifications.
iv © ISO 2004 – All rights reserved

ISO 19739:2004(E)
Introduction
Sulfur compounds may occur naturally in natural gas and remain as traces after treatment, or they may have
been injected deliberately to allow subsequent olfactory detection for safety reasons.
The standardization of several methods for the determination of sulfur compounds in natural gas is necessary
in view of the diversity of these compounds (hydrogen sulfide, carbonyl sulfide, tetrahydrothiophene, etc.) and
the requirements of the determinations (e.g. required uncertainty, measurement at the drilling head, clean-up
plant or in transmission pipes).
In order to enable its user to choose the most appropriate method for his/her particular needs and perform the
measurements under the best conditions, this International Standard gives the requirements needed to
perform a sulfur analysis.
INTERNATIONAL STANDARD ISO 19739:2004(E)

Natural gas — Determination of sulfur compounds using gas
chromatography
WARNING — Some sulfur compounds can constitute a serious health hazard.
1 Scope
This International Standard specifies the determination of hydrogen sulfide, carbonyl sulfide, C to C thiols,
1 4
sulfides and tetrahydrothiophene (THT) using gas chromatography (GC). Depending on the method chosen
from those given in the annexes, the application ranges for the determination of sulfur compounds can vary,
but whichever of the methods is used, the requirements of this International Standard apply.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 5725-2:1994, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic
method for the determination of repeatability and reproducibility of a standard measurement method
ISO 6141, Gas analysis — Requirements for certificates for calibration gases and gas mixtures
ISO 6143, Gas analysis — Comparison methods for determining and checking the composition of calibration
gas mixtures
ISO 6145-10, Gas analysis — Preparation of calibration gas mixtures using dynamic volumetric methods —
Part 10: Permeation method
ISO 10715:1997, Natural gas — Sampling guidelines
ISO 14532:2001, Natural gas — Vocabulary
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
alkane thiol
alkyl mercaptan
organic sulfur compound with the general formula R-SH (where R is the alkyl group), either naturally present
or added as an odorant to natural gas
[ISO 14532:2001, definition 2.5.3.3.1]
EXAMPLE Methanethiol (MeSH), ethanethiol (EtSH), 2-methylpropane-2-thiol (tert-butylmercaptan TBM).
ISO 19739:2004(E)
3.2
alkyl disulfide
organic sulfur compound with the general formula R-S-S-R′ (where R and R′ are alkyl groups)
[ISO 14532:2001, definition 3.5.3.3.3]
3.3
alkyl sulfide
thioether
organic sulfur compound with the general formula R-S-R′ (where R and R′ are alkyl groups), either naturally
present or added as an odorant to natural gas
[ISO 14532:2001, definition 3.5.3.3.2]
EXAMPLE Dimethyl sulfide (DMS), diethyl sulfide (DES).
3.4
carbonyl sulfide
COS
sulfur compound found in natural gas, which contributes to the total sulfur content
[ISO 14532:2001, definition 3.5.3.3.4]
3.5
chromatographic resolution
column efficiency characteristic describing the degree of separation of two adjacent peaks in gas
chromatography
[ISO 14532:2001, definition 2.5.3.4.6]
NOTE The resolution is measured as twice the distance between the maximum of the named peaks divided by the
sum of the intercepts on the baseline made by tangents drawn to the peaks at half the height.
3.6
cyclic sulfide
thioether
cyclic organic sulfur compound with one sulfur atom incorporated in a saturated hydrocarbon ring
EXAMPLE Tetrahydrothiophene (thiophane or thiacyclopentane, THT), i.e. C H S, which is added as an odorant to
4 8
natural gas.
[ISO 14532:2001, definition 2.5.3.3.6]
3.7
hydrogen sulfide
H S
colourless, toxic gas with an odour similar to rotten eggs
[ISO 14532:2001, definition 2.5.3.3.8]
3.8
normal reference conditions
reference conditions of pressure, temperature and humidity (state of saturation) equal to 101,325 kPa and
273,15 K for a dry, real gas
[ISO 14532:2001, definition 2.6.1.3]
2 © ISO 2004 – All rights reserved

ISO 19739:2004(E)
3.9
standard reference conditions
reference conditions of pressure, temperature and humidity (state of saturation) equal to 101,325 kPa and
288,15 K for a dry, real gas
[ISO 14532:2001, definition 2.6.1.4]
3.10
total sulfur
total amount of sulfur found in natural gas
[ISO 14532:2001, definition 2.5.3.3.17]
NOTE The total amount of sulfur may be determined by an analytical method not differentiating between individual
sulfur compounds.
3.11
working reference gas mixture
WRM
working standard gas mixture
gas mixture whose component quantity levels have been validated by direct comparison with a secondary
standard gas mixture (CRM)
[ISO 14532:2001, definition 2.5.3.5.2.3]
3.12
secondary standard gas mixture
gas mixture whose component quantity levels have been validated by direct comparison with a PSM
[ISO 14532:2001, definition 2.5.3.5.2.2]
3.13
primary standard gas mixture
PSM
gas mixture whose component quantity levels have been determined with the utmost accuracy and can be
used as a reference gas for determining the component quantity levels of other gas mixtures
[ISO 14532:2001, definition 2.5.3.5.2.1]
4 Principle
All significant components or groups of components to be determined in a gaseous sample are physically
separated by means of gas chromatography (GC) and measured by comparison with calibration or reference
gases. The gas being used for calibration and the sample gas shall be analysed with the same measuring
system under the same set of conditions
5 Apparatus
5.1 Gas chromatograph, containing injection device, oven, regulation system for temperature control and
pressure, detector.
5.2 Chromatographic columns, with column tubing made of a material inert to sulfur compounds (see 6.4),
and a stationary phase able to separate the sulfur compounds to be analysed in order that the resolution
between two adjacent peaks shall not be less than 1,5.
NOTE 1 See Annex A for a list of chromatographic columns mostly used in sulfur analysis.
NOTE 2 The absence of chromatographic separation between COS and H S will lead to an error in total sulfur amount
calculation.
ISO 19739:2004(E)
5.3 Detectors for detecting sulfur compounds:
 sulfur-specific,
 multi-specific (respond to halogen, sulfur), and/or
 general detectors.
See Annex B for descriptions of suitable detectors.
NOTE 1 Separation problems on a column could be solved by using a sulfur-specific detector, as hydrocarbons will not
be seen by it.
NOTE 2 Matrix effects can occur in sulfur analysis with certain methods/detectors.
NOTE 3 Sulfur response can be affected by quenching effects produced by hydrocarbons.
NOTE 4 Many detectors use an excited state of a molecule or atom to detect sulfur. An atom or molecule with one
electron shifted from its normal orbit to another (more energetic) is said to be excited. When it relaxes, returning to its
normal state, the electron falls back to its normal orbit emitting a photon. The energy of this photon is relative to the
difference in energy between the orbits. The wavelength of the photon is specific for each excited state. So, if photons of
different wavelength are separated (by a filter, monochromator, diffraction prism, etc.), the amount of specific photons can
be measured.
6 Sampling
The sampling procedures are very important in the analysis of sulfur compounds. Sulfur compounds have a
strong tendency to adsorb on to, or to chemically react with, different materials of construction. Low contents
of sulfur compounds in samples and calibration gas mixtures place demands on the sampling procedure to
ensure that the sulfur compounds in correct quantity reach the analytical detector.
Carry out representative sampling in such a way that the sample represents the bulk of the gas at the time of
sampling. Sampling and sample transfer shall be in accordance with ISO 10715.
Purge time should be long enough to have replicate stable analytical results within the acceptable standard
deviation of the analyser. Purge time needed will depend on the type and concentration of the sulfur
compound, materials of construction in gas contact and the gas flow through the sample loop.
6.1 Safety precautions
Safety precautions required in handling gas cylinders with pressurised flammable gas mixtures are described
in the ISO 10715. If a pressure regulator is to be connected to the cylinder, always use a regulator with
materials of construction recommended by the producer of the calibration gas.
6.2 Temperature control
When a cylinder of a calibration or sample gas mixture arrives at the place of use, ensure that the cylinder
temperature is kept above the condensation temperature (as stated on the certificate). If condensation may
have occurred during transportation or storage, store the cylinder at ambient temperature in a horizontal
position for at least 7 days. Rolling of the cylinder will lower the homogenisation time.
Always store both calibration and sample gases at the same suitable temperature.
To reduce any adsorption of low concentration levels of sulfur compounds when using the calibration gas or a
sample, the transfer lines from the cylinder and the bypass injection valve should be heated (to, for example,
90 °C).
4 © ISO 2004 – All rights reserved

ISO 19739:2004(E)
6.3 Construction materials
The presence of sulfur compounds in the calibration or sample gas makes the choice of materials of
construction in the pressure reduction device, the transfer line, the sample loop and the separation column
very important. The general considerations of ISO 10715 should always be followed.
6.4 Cleanness
When a calibration or sample gas cylinder is to be connected to a gas system, always inspect visually the
connection on the cylinder valve outlet. Carefully clean out any dirt, dust or particles with a dust-free cloth. Any
trace of humidity is to be purged out with dry inert gas.
Make sure that all transfer lines are free of dirt, rust, grease or other particles. Change all tubing/fittings if
there is any suspicion of impurities. Particle filters may be helpful, but they shall only contain material
proposed in ISO 10715.
6.5 Installation of the calibration gas cylinder
The installation of a calibration gas cylinder and use of the certified gas mixture is dependent on the method
by which a gas sample is taken and is to be analysed/compared. To minimise the surface in gas contact, it is
important to connect the calibration gas as near as possible to the injection point. One principle for the
connection of a calibration gas cylinder in direct sampling is shown in ISO 10715:1997, Annex A.
6.6 Pressure control
As described for the sample handling in ISO 10715, very often a pressure reduction device is required in order
to feed the calibration and sample gas to an analyser. Normally, this is a reduction valve connected directly or
close to the calibration and sample gas cylinder. Only use a pressure regulator made of the material approved
by the producer of the calibration gas mixture.
To further minimise any adsorption effects, a fine regulating needle valve (made in approved material) could
be connected directly to the cylinder valve. Be sure that the certified pressure range of this valve suits that of
the total system and that no local or national safety regulation prohibits such an arrangement.
Never use a calibration gas mixture with a total pressure lower than that recommended on the certificate. If no
recommendation is stated, stop using the mixture if the total pressure is lower than 10 % of the certified filling
pressure.
Always use the same reduced pressure when injecting the calibration mixture and the natural gas sample.
Control the purge flow by a needle valve, not by adjusting the reduction pressure valve.
If several calibration gases with different concentrations of the sulfur compounds are used, it is very important
to always use the same needle valve for the same calibration gas mixture. Be aware of the need to change
needle valves to different concentration levels.
6.7 Purging of reduction valve and transfer lines
Due to the strong tendency of sulfur compounds to adsorb to different materials of construction, it is important
to purge all surfaces (which are in contact with the gas) from the cylinder valve to the injection point. Using a
pressure-reducing valve mounted directly onto the cylinder valve connection, the purging should include a
number of “fill and empty” cycles as described in ISO 10715. A good practice is also to connect the total
transfer line from the reducing valve to vent and include the purge all the way through the sample loop.
When analysing calibration gases with different concentration levels, always flush the transfer lines and the
valves with dry N in order to avoid memory effects.
ISO 19739:2004(E)
6.8 Flow control
As stated in ISO 10715, turbulent flow is advantageous in a sampling system. The flow rate of the calibration
gas with 3,175 mm (1/8 in) tubing should at least be 80 ml/min to 100 ml/min. When purging a calibration gas
for analytical comparison with natural gas samples, the flow rate should be the same as the sample gas flow
rate.
With light gases like H or He in the calibration gas mixture, it may be of importance that the purge flow rate of
calibration gas mixtures is never below 10 ml/min, in order to avoid separation effects of lighter versus heavier
gases (effusion).
Stopping of flow just before injection of the standard/sample is the best way to minimize differences in the
injected gas volumes due to back-pressure variations. However, be aware of any change in atmospheric
pressure during the total analysis.
6.9 Diffusion control
Any leakage caused by diffusion of air-in or gas mixture out should be avoided by using pressure regulators
with non-permeable membranes.
Be aware that using polymer types of tubing in gas transfer lines may cause problems related to diffusion of
humidity from the environmental air.
6.10 Automation and sequences of sampling
With repeated injections and in order to get stable response from each sulfur compound in calibration and
sample gas mixtures, a programmable automatic gas sampling valve should be installed and used. Normally,
the tendency is that, due to adsorption phenomena, the peak from some sulfur compounds increases during
the first injections, but after a few repeated injections the peak areas become more and more stable. The
number of repeated injections required is to be defined based on achieved areas from each sulfur compound.
Repeated injections of the same calibration mixture before and after comparison analysis with one or more
samples gives a good indication of any drift in the detector response during the total analytical time.
7 Calibration
Perform regular calibration using working standard gas mixtures certified in accordance with ISO 6143 or
permeation devices according to ISO 6145-10. The working standard gas mixtures shall contain appropriate
number and concentrations of sulfur compounds in methane or natural gas depending upon the detector
characteristics (e.g. hydrocarbon quenching). A certificate of mixture according to ISO 6141 should always be
available with the cylinder.
NOTE 1 Sulfur compounds at low concentrations in gas mixtures are easily lost by sorption or reaction. The
preparation of such mixtures requires that extreme care be taken with the cleanliness of the surfaces of cylinders and of
tubing used for transfer, with the purities of the components used, particularly the matrix gas, and with the preparation
procedure. Stability of the mixture can be demonstrated by regular repeat analyses of the contents, using as reference a
dynamically prepared mixture of similar composition. A demonstrated history of preparation of mixtures which have been
successfully assessed for stability is the best form of assurance for the user.
NOTE 2 Another problem with diffusion is caused by connecting reduction valves to the cylinders. The air contained in
the reduction valve will diffuse into the cylinder when the cylinder value is opened while the reduction valve is still closed.
The oxygen will, for example, oxidize mercaptans to disulfides.
8 Analysis
Perform quantitative analysis and determine the mass concentration and uncertainty budget of the different
sulfur compounds in natural gas in accordance with ISO 6143.
6 © ISO 2004 – All rights reserved

ISO 19739:2004(E)
Be aware of the special adsorption and/or chemical problems that can occur with the handling of sulfur gas
components. Repeated injections of the same working reference gas mixture before and after comparison
analysis may give an indication of any drift due to sulfur adsorption during the total analytical time.
9 Performance characteristics required for sulfur analysis
The performance characteristics required for sulfur analysis were determined from a proficiency test
performed by seven laboratories in different countries. The following two mixtures — given here with their
compound/IUPAC name and mass concentration expressed in milligrams per cubic metre (under normal
reference conditions) — were analysed.
a) Mixture 1
 Hydrogen sulfide (HS): 3 mg/m
 Methane (CH): matrix
b) Mixture 2
 Carbonyl sulfide (COS): 5 mg/m
 Methanethiol (MeSH): 5 mg/m
 Ethanethiol (EtSH): 5 mg/m
 2-Methylpropane-2-thiol (TBM): 6 mg/m
 Diethyl sulfide (DES): 10 mg/m
 Tetrahydrothiophene (THT): 25 mg/m
 Methane (CH): matrix
The seven laboratories used different methods and calibration gases. The data obtained are given in Table 1.
Table 1 — Performance characteristics for sulfur analysis
Compound Mass concentration Achievable Achievable Proficiency
(sulfur compound in repeatability repeatability agreement
methane) (absolute) (relative) (relative)
3 3
% %
mg/m (norm. ref. cond.) mg/m (norm. ref. cond.)
H S 3 0,1 3 25
COS 5 0,1 2 15
MeSH 5 0,1 2 10
EtSH 5 0,2 4 30
TBM 6 0,4 7 25
DES 10 0,2 2 20
THT 25 1,0 4 20
ISO 19739:2004(E)
Proficiency agreement values quoted in Table 1 were calculated based on z-scores as defined in
Reference [5] (see 4.1, 4.2, 4.3), and are the limits between which two laboratories shall be able to achieve a
result of analyzing a known standard using different methods and calibration gases. The two laboratories
analyze a standard of known mass concentration of 25 mg/m of THT. If their results lie within the range of
3 3 3 3
19 mg/m and 31 mg/m , then they are comparable, i.e. 25 mg/m ± 5 mg/m (20 % of the proficiency
agreement given in Table 1) ± 1 mg/m (4 % of the achievable repeatability given in Table 1).
The repeatability shown in Table 1 was calculated in the following way: two times the standard deviation
based on n−1 values (95 % confidence interval, see ISO 5725-2), free of outliers (see ISO 5725-2:1994,
7.3.4.1), assuming a normal distribution calculated with 5 analyses.
10 Test report
The test report shall include at least the following information:
a) reference to this International Standard and the analytical method used;
b) sample identification including
 time/date of the sampling,
 sample point/stream (location), and
 cylinder identification (for spot sampling);
c) reference to the calibration system used;
d) sample mass concentration, including the number of digits appropriate to the certificate of WRM and size
of error, including the result of uncertainty calculation;
e) comments, including
 any deviation from specified procedure, and/or
 problems concerning the sample;
f) date of analysis, name of laboratory and signature of analyst.

8 © ISO 2004 – All rights reserved

ISO 19739:2004(E)
Annex A
(informative)
Columns mostly used in sulfur analysis (with internal phase and
dimensions)
Film
thickness of
stationary
Stationary phase Dimensions Type Compounds
phase
df
µm
100 % dimethylpolysiloxane 50 m × 0,32 mm Capillary 5 Hydrogen sulfide, mercaptans,
carbonyl sulfide, diethyl sulfide,
dipropyl sulfide
100 % dimethylpolysiloxane Capillary 4 Hydrogen sulfide, carbon
30 m × 0,32 mm
disulfide, sulfur dioxide
Porous layer open tubular 30m × 0,32 mm Capillary 4 Hydrogen sulfide, carbonyl
sulfide, mercaptans
Styrene-divinylbenzene polymer 30 m × 0,32 mm Capillary 10 Hydrogen sulfide, carbonyl
sulfide, methyl sulfide,
mercaptans,
tetrahydrothiophene
5 % phenyl-95 % dimethylpolysiloxane Capillary 5 Hydrogen sulfide, mercaptans,
25 m × 0,53 mm
carbon disulfide, carbonyl
sulfide, dimethyl disulfide,
dimethyl sulfide, sulfur dioxide,
thiophene
50 % phenyl 50 % dimethylpolysiloxane 1,5 m × 3,175 mm Packed 80 to 100 Hydrogen sulfide, carbonyl
mesh sulfide, mercaptans
(1/8 in)
100 % dimethylpolysiloxane Packed 80 to 100 Hydrogen sulfide, carbonyl
1,5 m × 3,175 mm
mesh sulfide
(1/8 in)
40 % dynonyl phthalate 30 cm — 80 to 100 Tetrahydrothiophene,
mesh mercaptans
NOTE This is not an exhaustive list. Recent developments could lead to other columns being available.

ISO 19739:2004(E)
Annex B
(informative)
Types of detectors used in sulfur analysis
B.1 General
For a summary of the characteristics of the types of detectors described here, see Table B.1.
B.2 Atomic emission detector (AED)
The effluents of the gas chromatograph come into a cavity where a plasma is induced and sustained by
different energy forms (mostly by microwave induction). The photons emitted by the relaxing atoms may then
be separated by wavelength and measured. This detector is specific for different atoms.
See Annex F.
B.3 Electrochemical detector (ED)
The effluents of the gas chromatograph are gently blown on the surface of an electrolyte where sulfur
compounds react. This reaction induces an electron flow (redox reaction). Two electrodes dip into the
electrolyte to measure this induced current. This detector is multi-specific for different compounds, depending
on the chosen electrolyte.
See Annex D.
B.4 Electron capture detector (ECD)
The electron capture detector contains a radioactive source used to create an electron flow. This flow is
measured by electrodes. When the effluents of the gas chromatograph pass through this cell, some electrons
might react with the effluents, thus changing the measured current (DC voltage mode). The specificity
depends on the differences of compound affinity for electrons. Response is then strongly compound-
dependent.
B.5 Flame photometric detector (FPD)
The effluents of the gas chromatograph are burnt into an FID type flame with specific H /air ratios. When so
burned, sulfur and phosphorus containing hydrocarbons will produce fluorescent species (which can be
compared to an excited molecule). During the relaxation of these species, specific photons will be emitted.
These are separated by an optical filter and can then be measured. Many variations exist (single-flame, dual-
flame, linearized response, pulsed). This detector is specific. There are known interferences (quenching) with
hydrocarbons, the response is non-linear but often can be electronically corrected. New developments of this
detector are made to limit these problems.
See Annexes C and G.
10 © ISO 2004 – All rights reserved

ISO 19739:2004(E)
B.6 Pulsed flame photometric detector (PFPD)
Like the FPD, this detector uses a flame, but it can provide better sensitivity and selectivity for sulfur and
phosphorus. Two different combustible gas flows enter the bottom of the combustion chamber through narrow
gas lines (the FPD, in contrast, has only one). The second incoming gas flow’s job is to help fill up the outer
volume of the combustion chamber while the analyte and the primary combustion gas flow into that chamber.
This second flow also helps to optimize the analyte emission brightness in the combustion process. At the top
of the PFPD is an ignition wire which stays continuously red-hot. Then the gases flowing into the combustor
including the analytes exiting the GC column reach a flammable mixture they are ignited by the ignition wire
and the flame propagates back down the combustor. The flame front terminates, i.e. it uses up all of the
quickest-burning flammable material in the combustor, in less than 10 ms and the flame goes out. And it is
after this short flame pulse that the slower-burning analytes are excited and emit the light that is characteristic
of their elements. During this period, the photomultiplier records the arrival of the analyte’s light from the
combustion chamber. After about 300 ms, the flame pulses again as new flammable material fills the
combustion chamber from the inlet tubes and GC column and that combination once again constitutes a
flammable mixture. In this way, about three flame pulses are recorded per second.
See Annex I.
B.7 Hall-electrolytic conductivity detector (ELCD or HELCD)
The effluents of the gas chromatograph are mixed with a reaction gas in a reaction tube. The resulting
products are then mixed with deionised solvent. The conductivity is then measured. This detector is multi-
specific (halogens, sulfur, nitrogen containing compounds), depending on the absorbing solvent selected.
B.8 Mass selective detector (MSD)
The effluents of the gas chromatograph are bombarded with electrons, which provoke bond ruptures and
molecule ionization. The ions are then accelerated and placed into a magnetic field. The radii of their path is a
function of their mass. Many theories describe the ionization of molecules. The ion proportions produced by
different molecules are different. The detection is mass specific.
See Annex E.
B.9 Photoionization detector (PID)
The effluents of the gas chromatograph are excited by the photons of a UV lamp and ionized. The resultant
charged particles are measured between two electrodes. This detector is multi-specific for different
compounds, depending on the chosen lamp for excitation and ionization potentials of compounds. Only used
for H S.
B.10 Thermoionization detector (TID)
Similar to the photoionization detector but the ionization is caused by high temperatures.
B.11 Sulfur chemiluminescence detector (SCD)
The effluents of the GC are mixed with reactive compounds and will form excited species which will relax
emitting photons. Usual sulfur chemiluminescence detectors use ozone under reduced pressure. This detector
is specific.
See Annex H.
ISO 19739:2004(E)
B.12 Thermal conductivity detector (TCD)
The effluents of the gas chromatograph pass through a cell where a filament is heated. Another cell flushed by
a reference gas homes a second filament. The two filaments are part of a Wheatstone bridge. If the effluents
contain products with a different thermal conductivity than the reference gas, a current will be induced in the
bridge. This signal is then measured. This detector is non-specific.
B.13 H S lead acetate detector
The effluents react in a high temperature hydrogenator, assuming that sulfur compounds are transformed into
hydrogen sulfide. The effluents then pass through a lead acetate treated paper which will react with H S so
produced. Optical measurement of the darkening of the tape is used to detect the sulfur compounds. This
detector is specific.
Table B.1 — Detectors and their characteristics
Detector Specificity Detection Linearity Interferences Main use Remark
limit
a b
++++ +++++ Unknown Element specific Multi-purpose
AED +++++
a
++++ +++ ++++ Unknown Electrolyte specific —
ED
c d
ECD ++++ Possible Halogens Radioactive
variable variable
a
++++ to +++++ ++ to ++++ ++ to ++++ Hydrocarbons Sulfur, phosphorus Widely used
FPD
HELCD or ++++ +++ +++ to +++++Possible Halogens —
ELCD
a
non-specific +++ ++ to ++++ Unknown All organic compounds Multi-purpose
MSD
PID + ++++ +++++ Possible Aromatics, inorganic —
compounds
TID — — — Possible — —
a
+++++ +++++ ++++ Unknown Sulfur compounds Low detection
SCD
limit
TCD non-specific ++ +++ Yes — Non-selective
H S +++++ — — — — —
lead acetate
+ Not very specific.
++++ Specific but can detect other non-sulfur compounds with less sensitivity.
+++++ Very specific — detects only compounds containing sulfur.
a
Detectors used in the proficiency test.
b
Best.
c
Depends on the application (only H S or all compounds).
d
Depends on the application (only H S or all compounds).
12 © ISO 2004 – All rights reserved

ISO 19739:2004(E)
Annex C
(informative)
GC method using capillary column and FPD
C.1 Application
This method specifies the conditions for the qualitative and quantitative analysis of sulfur compounds in
3 3
natural gas at a mass concentration level of 0,5 mg/m up to about 600 mg/m (at normal reference
conditions) by gas chromatography.
An application example for this working instruction is the quality control of natural gases, including the analysis
of the following components:
 Hydrogen sulfide (H S) (lower limit of concentration range 1 mg/m at normal reference conditions);
 Carbonyl sulfide (COS);
 Methane-, ethane-, 2-methylpropane-2-thiol (tert-butyl mercaptan) (MeSH, EtSH, TBM);
 Diethyl sulfide (DES);
 Tetrahydrothiophene (THT, C H S).
4 8
C.2 Apparatus
C.2.1 Gas chromatograph, containing a capillary fused silica column (styrene-divinylbenzene polymer).
C.2.1.1 Sample injection device: gas sampling valve, capable of operating in a split/splitless mode
with a sample loop of 2 ml. Set the split flow rate at 15 ml/min. To avoid adsorption and desorption
phenomena, the use of metal in this part of the apparatus should be restricted.
C.2.1.2 Column of fused silica, having a length of 30 m, internal diameter of 0,32 mm, and packing
made of styrene-divinyl benzene polymer with a film thickness of 10 µm.
C.2.2 Flame photometric detector (FPD) (see Figure C.1)
The colu
...