Overview - EN ISO 10101-1:2022 (Natural gas / Karl Fischer)
EN ISO 10101-1:2022 specifies the general requirements for determining water in natural gas using the Karl Fischer (KF) method. It is the Part 1 document in the ISO 10101 series and sets the framework for the two specific analysis techniques defined in companion standards: ISO 10101-2 (volumetric/titration) and ISO 10101-3 (coulometric). The standard is intended for laboratories, gas producers, transmission/distribution operators and testing bodies performing moisture analysis on natural gas.
Key topics and technical requirements
- Scope and principle: Defines the KF reaction basis (iodine / sulfur-dioxide in methanol or related reagents) and the stoichiometric relation between iodine and water used to calculate moisture content.
- Two KF techniques:
- Volumetric (titration) - recommended for larger water amounts (suitable range noted in the ISO introduction).
- Coulometric - micro-method ideal for very low water quantities; iodine is generated electrochemically.
- Reactions and interferences:
- Identifies gas constituents that can interfere (oxidizing/reducing agents, H2S, mercaptans, basic nitrogen compounds).
- Provides guidance on correcting for hydrogen sulfide and mercaptan interference when their concentrations are below certain limits; recommends sulfur-speciation measurement methods (e.g., gas chromatography – see ISO 19739).
- Sampling requirements:
- Sampling to follow ISO 10715 guidelines.
- Maintain gas temperature above dew point; heat sampling equipment if necessary.
- Materials in contact with the gas should be steel, glass or suitable inert materials; connectors often use fluoroelastomers.
- Measurement uncertainty:
- Recommends estimating uncertainty from interlaboratory comparison data (ISO 5725-2) and applying guidance in ISO 21748; expanded uncertainty (k=2) is used for reporting.
Applications and who uses it
- Quality control and custody transfer testing for natural gas moisture content.
- Engineering and operations teams monitoring pipeline condition, preventing hydrate formation and corrosion.
- Analytical and testing laboratories performing KF titration or coulometry for gas analysis.
- Manufacturers of gas analyzers and sampling equipment that must meet standardized sampling and measurement practices.
Related standards
- ISO 10101-2 - Karl Fischer titration procedure for natural gas
- ISO 10101-3 - Karl Fischer coulometric procedure for natural gas
- ISO 10715 - Natural gas sampling guidelines
- ISO 14532 - Natural gas vocabulary
- ISO 19739 - Methods for sulfur compounds (relevant for interference correction)
- ISO 5725-2 / ISO 21748 - Guidance on measurement uncertainty and validation
This standard is essential for consistent, accurate water determination in natural gas using the Karl Fischer method and for ensuring comparable results across laboratories and the gas supply chain.
