Overview
ISO/TS 17764-2:2002 - "Animal feeding stuffs - Determination of the content of fatty acids - Part 2: Gas chromatographic method" specifies a validated gas‑chromatographic procedure for quantifying individual fatty acids in fats, oils and fat extracts used in animal feeding stuffs. The method uses fatty acid methyl esters (FAMEs) prepared according to ISO/TS 17764-1 and separates them on capillary columns with flame ionization detection (GC‑FID). It applies to animal and vegetable fats and fatty acid mixtures (including those containing butyric acid) but is not applicable to polymerized fatty acids.
Key topics and technical requirements
- Analytical technique: Gas chromatography with capillary columns and flame ionization detector (GC‑FID).
- Sample prep: FAMEs must be prepared as per ISO/TS 17764-1.
- Columns and separation: Capillary columns (fused silica or glass) with chemically bonded stationary phases are recommended. Resolution of at least 1.25 between C16:0/C16:1 and C18:0/C18:1 is expected. Moderately polar phases are typical; more polar phases may be used for cis/trans or positional isomer separation.
- Injection options: Split, split‑less or cold on‑column injectors. Notes: warm split‑less injectors can interfere with butyric acid analysis; cold on‑column requires n‑pentane for short‑chain FAMEs. Suggested split ratios are 1:30 to 1:100 for split injection.
- Solvents and reagents: Analytical grade solvents (n‑hexane, n‑heptane, n‑pentane) and water complying with ISO 3696. Reference mixtures or certified FAME standards are required for identification and calibration.
- Quantification: Use of an internal standard (commonly C17:0) and relative calibration factors. Calibration factors for short‑chain FAMEs must be determined (selective evaporation and extraction issues are discussed). Relative calibration factors should not deviate more than 5% from theoretical response factors.
- Operating parameters: Injector and oven programming guidance (e.g., start oven at ~60 °C when short‑chain fatty acids are present). Detector temperature should be 20–50 °C above the highest column temperature and at least 150 °C. Typical injection volumes: 0.1–1 µL; sample dilution varies by injector type (≈1% mass fraction for split, ≈0.05% for split‑less/cold on‑column).
- Performance: Precision established through interlaboratory studies per ISO 5725; repeatability and reproducibility limits are provided in the standard.
Applications and users
- Quality control laboratories in animal feed and oilseed processing
- Feed manufacturers and formulation chemists verifying fatty acid profiles for nutrition and labeling
- Regulatory and certification bodies testing raw materials and finished feeds
- Research labs studying lipid composition, digestion, or supplementation (e.g., butyric acid content)
Related standards
- ISO/TS 17764-1:2002 - Preparation of methyl esters (required companion document)
- ISO 3696 - Water for analytical laboratory use
- ISO 5725 - Method precision (interlaboratory study guidance)
Keywords: ISO/TS 17764-2:2002, fatty acids, animal feeding stuffs, gas chromatography, GC‑FID, methyl esters, capillary column, feed quality, fatty acid profile.