ISO 10101-3:2022

Overview

ISO 10101-3:2022 - Natural gas - Determination of water by the Karl Fischer method - Part 3: Coulometric procedure specifies a coulometric Karl Fischer (KF) titration technique for measuring water content in natural gas and other gases that do not react with KF reagents. The standard covers measurements over the range 5 mg/m3 to 5 000 mg/m3, with volumes expressed at 273.15 K (0 °C) and 101.325 kPa (1 atm). It defines the coulometric principle, apparatus, reagents, sampling, test procedure, blank correction and result expression including measurement uncertainty.

Key topics and technical requirements

• Method principle: Coulometric KF titration - iodine generated electrochemically; charge passed is proportional to water mass via Faraday’s law.
• Applicable range: 5 mg/m3 to 5 000 mg/m3 (water in gas).
• Reagents: Coulometric-specific reagents; for diaphragm cells use separate anolyte and catholyte. Recommended reference solution examples given (e.g., 10 mg/g ±1 % or alternatives 5.0 mg/l ±4 % / 10.0 mg/l ±4 %).
• Cell designs: Cells with diaphragm (anode/cathode compartments) and without diaphragm - advantages and trade-offs are discussed.
• Apparatus: Titration cell, gas inlet with 3‑way valve, drying tube, platinum electrodes, stirrer; wet-test gas meter or equivalent (accuracy ±1 %) to measure volume.
• Operational parameters: Typical gas flowrate guidance 30–40 L/h (optimum depends on equipment geometry). Equilibration and drift checks required before measurement.
• Blank correction: Required for low water concentrations (<100 mg/m3) to correct iodine losses during gas passage.
• Quality controls: Response testing by injecting known reference solution volumes; measurement uncertainty addressed (subclause 9.2).
• Safety note: Account for local safety regulations when equipment is in hazardous areas.

Applications and users

ISO 10101-3:2022 is intended for:

• Gas analysis laboratories performing water-in-gas testing using Karl Fischer coulometry.
• Natural gas producers, pipeline and transmission operators for monitoring moisture content and process control.
• Instrument manufacturers and calibration services developing or validating coulometric KF equipment.
• Use cases include routine moisture analysis, quality control, leak detection support, and laboratory method validation for gases that are inert to KF reagents.

Keywords: ISO 10101-3:2022, Karl Fischer coulometric, natural gas water determination, water content in gas, KF titration, gas analysis, measurement uncertainty.

Related standards

• ISO 10101-1 - Natural gas - Determination of water by the Karl Fischer method - Part 1: Introduction (referenced normative guidance).
• ISO 14532 - Natural gas - Vocabulary (terms and definitions used).

For implementation, follow the standard’s procedures for sampling, reagent handling, blank correction and documentation of test reports.