Overview
ISO 8420:2002 specifies a laboratory method for determining the content of polar compounds in animal and vegetable fats and oils. Polar compounds form when fats and oils deteriorate during heating (for example, frying). Measuring polar compound content helps assess frying-oil quality and the extent of thermal degradation.
Key topics and technical requirements
- Principle: Separation of a test portion by column chromatography into non‑polar (mainly triglycerides) and polar fractions; non‑polar fraction is collected and weighed, and polar content is calculated by difference.
- Test portion: Typically (2.5 ± 0.1) g sample dissolved to make a 50 ml test solution; 20 ml of this is applied to the column.
- Column and packing: Glass column (≈21 mm ID × 450 mm) packed with 25 g silica gel conditioned to 5% water content; sand and cotton wool used as support layers.
- Elution solvent: Mix of light petroleum (40–60 °C) and stabilized diethyl ether (87:13 by volume). Elution of non‑polar compounds uses 150 ml solvent passed through the column in 60–70 minutes.
- Solvent removal and drying: Evaporate solvent under reduced pressure with bath temperature ≤ 60 °C; final drying at (103 ± 2) °C, with repeat weighings until mass change ≤ 1 mg.
- Result expression: Polar compound content expressed as mass fraction (%) calculated from flask masses and test portion; two determinations required and result given to one decimal place.
- Quality checks: Annex A describes thin‑layer chromatography to assess column efficiency. Annex B provides interlaboratory precision data (repeatability and reproducibility limits).
Safety note: diethyl ether can form explosive peroxides; ISO 8420 requires stabilized ether and low‑temperature evaporation.
Applications and users
ISO 8420 is used to:
- Monitor frying oil deterioration in foodservice and industrial frying operations.
- Support quality control in edible oil producers, refiners and packers.
- Provide test methods for food safety and regulatory laboratories assessing oil reuse and disposal suitability.
- Support research on lipid thermal degradation, frying practices, and shelf‑life.
Typical users: analytical laboratories, QC technicians, food manufacturers, regulatory agencies, and research institutions focusing on fat/oil chemistry and frying processes.
Related standards
- ISO 661 - Preparation of test sample (referenced normative).
- ISO 5555 - Sampling of animal and vegetable fats and oils (recommended).
- ISO 5725 - Accuracy (trueness and precision) of measurement methods and results - used for interpreting precision data in Annex B.
Keywords: ISO 8420, polar compounds, fats and oils, frying oil deterioration, column chromatography, fat quality testing, oil analysis, polar compounds content.
