ISO 24894

ISO/FDIS 24894:2025(en)
ISO /TC 193/SC 1/WG 24
Secretariat: NEN
Date: 2025-08-25
Analysis of natural gas — Determination of sulfur compounds— —
Determination of hydrogen sulfide by laser absorption spectroscopy
Analyse du gaz naturel — Détermination des composés soufrés — Détermination du sulfure d’hydrogène par
spectroscopie par absorption laser
FDIS stage
ISO/DIS 10360-102FDIS 24894:2025(en)
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Published in Switzerland
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ISO/FDIS 24894:2025(en)
Contents
Foreword . v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents and material . 3
6 Measurement device . 4
7 Sample . 4
8 Measurement . 4
9 Analysis . 5
10 Precision and measurement uncertainty . 5
11 Test report . 6
Annex A (informative) Example of statistical procedure for estimation of the repeatability . 7
Bibliography . 5

Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents and material . 2
5.1 Calibration gas . 2
5.2 Methane . 2
5.3 Absorption solution for hydrogen sulfide . 2
6 Measurement device . 3
6.1 General requirements . 3
6.2 Laser generator . 3
6.3 Pretreatment system . 3
6.3.1 Filter unit . 3
6.3.2 Pressure control unit . 3
6.3.3 Flow control unit . 3
7 Sample . 3
8 Measurement. 3
8.1 Preparation . 3
8.2 Calibration of analyser . 4
8.2.1 Calibration frequency . 4
8.2.2 Calibration procedure . 4
8.2.3 Calibration method . 4
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ISO/DIS 10360-102FDIS 24894:2025(en)
9 Analysis . 4
10 Precision and measurement uncertainty . 4
11 Test report . 5
Annex A(informative)Example of statistical procedure for estimation of the repeatability . 6
Bibliography . 9

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ISO/FDIS 24894:2025(en)
Foreword
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This document was prepared by Technical Committee ISO/TC 193, Natural gas, Subcommittee SC 1, Analysis
of natural gas.
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ISO/DIS 10360-102FDIS 24894:2025(en)
Introduction
Five methods for determination of sulfur compounds in natural gas already exist as International Standards:
ISO 16960, ISO 19739, ISO 20729, ISO 20676, ISO 11626.
Laser absorption spectroscopy is a more efficient method compared with chemical titration because it is an
optical and instrumental method. It offers a more convenient and more stable means to analyse H S in natural
gas.
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ISO/FDIS 24894:2025(en)
Analysis of natural gas — Determination of sulfur compounds—
— Determination of hydrogen sulfide by laser absorption
spectroscopy
1 Scope
This document describes a method for the online determination of hydrogen sulfide content in natural
gas by laser absorption spectroscopy. The analytical range expressed as mole fraction is 1 μmol/mol to
50 μmol/mol.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 6143, Gas analysis — Comparison methods for determining and checking the composition of
calibration gas mixtures
ISO 10715, Natural gas — Gas sampling
ISO 12963, Gas analysis — Comparison methods for the determination of the composition of gas mixtures
based on one- and two-point calibration
ISO 14532, Natural gas — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 14532 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— — ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
4 Principle
A sketch of the measuring principle is shown in Figure 1.Error! Reference source not found. The
semiconductor laser generator generates a laser beam: the laser beam goes through the sample in a gas
chamber and reflects many times between the high reflectivity mirrors at both ends. Then, the laser
beam is detected by the photoelectric sensor. The energy of the laser beam is attenuated because of the
absorption by the test sample. The absorbance obeys the Beer-Lambert law. which describes the
relationship between the absorbance and the mole fraction of (in this case) hydrogen sulfide.
𝑨 = 𝜺 ∙ l ∙ c                (1)
A: Absorbance
𝜺 : Molar absorption coefficient (M-1cm-1)
l : Optical path length (cm)
c : Molar concentration (mol/L or M)
ISO/DIS 10360-102FDIS 24894:2025(en)

a b
3 3
𝐴 = 𝜀 ·  𝑙  ·  𝑐 (1)
where
Key
A is the absorbance
-1 -1
1 ana is the molar absorption coefficient (M cm )
Inserted Cells
lyti
cal
unit
𝜀
2 laseis the optical path length (cm)
r
gen
erat
orl
3 mir is the molar concentration (mol/L or M)
ror
c
4 gas chamber
5 sensor
a
Gas input.
b
Gas output.
ISO/FDIS 24894:2025(en)
Key
1 analytical unit
2 laser generator
3 mirror
4 gas chamber
5 sensor
a
Gas input.
b
Gas output.
Figure 1 — Working principle of the hydrogen sulfide laser absorption analyser
5 Reagents and material
5.1 Calibration gas
Calibration shall be performed in accordance with ISO 6143. Hydrogen sulfide calibration gas mixtures
suitable for the instrument range shall be selected in accordance with the calibration method used.
The balance gas of the hydrogen sulfide calibration gas mixture shall be methane. A matrix of natural
gas may be used as the balance gas instead of methane.
...