ISO 16960:2014

Overview - ISO 16960:2014 (Natural gas - Determination of total sulfur by oxidative microcoulometry)

ISO 16960:2014 specifies an analytical method to determine total sulfur in pipeline natural gas using oxidative microcoulometry. The method covers the range 1 mg/m3 to 200 mg/m3; samples with higher sulfur content can be analysed after dilution with a suitable sulfur‑free solvent. The standard describes the test principle, required reagents and apparatus, sampling and injection procedures, calculation and quality checks necessary for reliable sulfur quantification.

Key technical topics and requirements

• Test principle: Sulfur compounds in a gas sample are converted to SO2 by oxidative pyrolysis in a quartz furnace. SO2 is titrated in an electrolyte containing iodine; consumed iodine is replenished by electrolysis of potassium iodide and quantified by microcoulometry. Sulfur mass is calculated from the measured electric charge (Faraday’s law) and corrected using a conversion factor from a reference standard.
• Measurement range: 1–200 mg/m3 (dilution recommended for higher concentrations).
• Reagents and gases: Grade 3 water (ISO 3696), glacial acetic acid, potassium iodide, oxygen (≥99.99% purity) and carrier gas (argon, helium or nitrogen ≥99.99%).
• Apparatus: quartz furnace with three heating zones (preheat ~800 °C, combustion ~900 °C, exit ~800 °C), titration cell with electrolysis and indicator electrodes, microcoulometer, flow controller, electromagnetic stirrer, calibrated syringes and volumetric flask.
• Calibration and validation: Use calibration gas mixtures prepared per ISO 6142 / ISO 6144 / ISO 6145; recommended reference species include COS or H2S. Determine and monitor the sulfur conversion rate (average of five consecutive runs with RSD ≤ 2%). Conversion rates below 75% require investigation.
• Sampling: Pipeline sampling follows ISO 10715; cylinder handling and syringe injection protocols are specified (injection speeds/volumes and syringe flushing).

Practical applications and users

• Industrial and laboratory analysis of pipeline natural gas quality for regulatory compliance, custody transfer, environmental reporting and process control.
• Users: gas analysis laboratories, pipeline operators, gas processors, QA/QC teams, environmental compliance officers, and instrument manufacturers supplying microcoulometric analyzers.
• Benefits: direct measurement of total sulfur (sum of sulfur species) without separate speciation, suitable for routine monitoring within the specified range.

Related standards

• ISO 6326-3 (potentiometry for H2S/mercaptans/COS), ISO 6326-5 (combustion), ISO 19739 (GC methods); ISO 3696, ISO 6142, ISO 6144, ISO 6145 and ISO 10715 are normative references for reagents, calibration gas preparation and sampling.

Keywords: ISO 16960:2014, natural gas, total sulfur, oxidative microcoulometry, microcoulometer, sulfur determination, pipeline natural gas, sulfur conversion rate, calibration gas.