ISO 32662-2:2025

Overview

ISO 32662-2:2025 - Liquid petroleum products - Determination of total contamination - Part 2: Fatty acid methyl esters (FAME) specifies a vacuum‑filtration method to measure total contamination (undissolved substances) in neat FAME. The method’s validated working range is 5 mg/kg to 27 mg/kg, established by an interlaboratory study using ISO 4259‑1. It is primarily applicable to FAME with kinematic viscosity ≤ 8 mm2/s at 20 °C (or ≤ 5 mm2/s at 40 °C, e.g. EN 14214), but can be used outside this range acknowledging that precision was not determined. The standard includes sampling, cleaning, filtration, drying and calculation procedures and carries a warning to observe appropriate safety practices.

Key topics and technical requirements

• Principle: weigh a test portion, filter under vacuum through a pre‑weighed glass‑fibre filter, wash, dry and re‑weigh. Calculate contamination as mg/kg of sample.
• Working range: 5–27 mg/kg (precision established by interlaboratory study).
• Viscosity applicability: generally for FAME ≤ 8 mm2/s (20 °C) or ≤ 5 mm2/s (40 °C); method may be used beyond these limits without validated precision.
• Filtration system: designed for 47 mm high‑retention glass fibre filters with ~0.7 µm mean pore size; membrane filters 0.45 µm referenced for other preparatory steps.
• Vacuum: absolute pressure 2 kPa to 5 kPa inside the filtration apparatus. (Water vacuum pumps excluded.)
• Cleaning and sample handling: strict cleaning (detergent, rinses with propan‑2‑ol and heptane) and controlled sample containers (glass, light protection, fill 80–85% capacity).
• Sample preparation: heat samples to 60 °C for ≥2 h to redissolve any separated components before homogenization.
• Equipment accuracy: analytical balance to 0.1 mg, top‑load balance to 0.1 g, ovens (110 ± 5 °C), desiccator with desiccant indicator.
• Reagents: heptane (≥99.0 % v/v) and propan‑2‑ol (≥99.0 % v/v).
• Precision reporting: repeatability (r) and reproducibility (R) are addressed where determined.

Applications and users

ISO 32662-2:2025 is intended for:

• Quality control laboratories at biodiesel and FAME producers
• Fuel testing houses and certification bodies
• Refineries and fuel distributors monitoring filter‑blocking contaminants
• Automotive and engine manufacturers verifying fuel cleanliness for hardware compatibility
• Regulatory authorities and purchasers requiring consistent contamination measurement

Practical uses include routine QC, batch acceptance testing, supplier verification, and investigations when filter plugging or unexpected system contamination occurs.

Related standards

• ISO 32662‑1 (method for middle distillates and diesel/FAME blends)
• ISO 4259‑1 (interlaboratory study procedures / precision estimation)
• EN 14214 (FAME fuel specification)
• ISO 3170 / ISO 3171 (sampling of hydrocarbon liquids)
• ISO 5164 (heptane as a reference fuel)

Note: The standard warns of hazardous materials and requires users to apply appropriate health, safety and regulatory controls.