ISO 12937:2000

Overview

ISO 12937:2000 specifies a laboratory method for the direct determination of water in petroleum products using the coulometric Karl Fischer titration. The method applies to petroleum fractions boiling below 390 °C and covers a water mass-fraction range of 0.003 % (m/m) to 0.100 % (m/m). It excludes products containing ketones and residual fuel oils. An informative alternative volumetric procedure for 0.003 % (V/V) to 0.100 % (V/V) is given in Annex B. Precision data are based on dual‑cell, dual‑electrolyte systems.

Key topics and technical requirements

• Principle: Coulometric generation of iodine; water quantified from integrated current (Faraday’s law).
• Scope limits: Applicable to petroleum products boiling < 390 °C; not for ketone-containing products or residual fuel oils; possible use for lubricating base oils (precision not established).
• Measurement range: 0.003 % to 0.100 % (m/m) water (alternative volume measurement in Annex B).
• Interferences: Common petroleum interferences include hydrogen sulfide and mercaptan sulfur - levels < 0.003 % (m/m) sulfur generally do not affect results. Sulfides, disulfides and thiophenes do not interfere.
• Chemicals & reagents: Dry xylene, molecular sieve (4A), Karl Fischer anolyte/catholyte or single KF solution, sodium dioctylsulfosuccinate (surfactant) and grade 3 water for checks.
• Apparatus: Automatic coulometric Karl Fischer titrator, non‑aerating mixer for homogenization, glass syringes, precision balance (±0.1 mg), ovens and sealed containers.
• Sample handling: Normative Annex A covers sampling, visual inspection (clear and bright vs. not), homogenization procedures when free water/particulates are present, and limits on mixing temperature rise.
• Quality control: Regular reagent and apparatus checks (e.g., 10 µL water injections) and replacement criteria for electrolytes; background current stability required.
• Safety note: Standard warns of hazardous materials and procedures; users must follow appropriate safety practices.

Applications and users

ISO 12937 is intended for:

• Petroleum testing laboratories performing moisture analysis and quality control.
• Refineries and fuel distribution labs monitoring fuel water content.
• Lubricant manufacturers evaluating base oils (with caution about precision).
• R&D and compliance labs where accurate low-level water determination in hydrocarbon matrices is required.

Keywords: ISO 12937, Karl Fischer titration, coulometric, water determination, petroleum products, moisture analysis, petroleum testing, lubricating base oils.

Related standards

• ISO 3170:1988 - Petroleum liquids - Manual sampling
• ISO 3171:1988 - Petroleum liquids - Automatic pipeline sampling
• ISO 3696:1987 - Water for analytical laboratory use - Specification and test methods

For implementation, follow the detailed procedures, apparatus checks and annex requirements in ISO 12937:2000 to ensure reliable, interference‑aware water measurements in petroleum matrices.