Overview
EN ISO 8294:1999 (ISO 8294:1994) specifies a validated analytical procedure for the determination of trace copper (Cu), iron (Fe) and nickel (Ni) in animal and vegetable fats and oils using graphite furnace atomic absorption spectrometry (GFAAS). The method is intended for quality control, regulatory compliance and research laboratories analyzing fats and oils where accurate trace-metal quantification is required.
Key Topics
- Principle: Vaporization of a test portion in a graphite furnace atomizer connected to an atomic absorption spectrometer and measurement of absorbance at metal-specific wavelengths.
- Target analytes and wavelengths:
- Copper (Cu): 324.7 nm
- Iron (Fe): 302.1 nm
- Nickel (Ni): 232.0 nm
- Sample types: Liquid and solid animal and vegetable fats and oils. Sample preparation follows ISO 661; do not filter the test sample.
- Critical reagents and materials:
- Aluminium oxide (analytical grade) for purification/columns
- Dilution oil (metal-free refined edible oil)
- Niobium solution for internal coating when measuring iron
- n-Heptane and argon (or nitrogen as purge gas when argon unavailable)
- Apparatus essentials: Polyethylene/polypropylene bottles, micropipettes (20 µL and 100 µL), pipette tips pretreated with n-heptane, electric oven (≈150 °C), GFAAS with appropriate lamps and background correction.
- Calibration and blanks: Use organometallic standard working solutions in dilution oil. Record a graphite-tube blank and a dilution-oil blank; generate calibration curves relating corrected absorbance to mg/kg metal.
Applications
- Routine quality control and acceptance testing for edible and industrial fats and oils
- Monitoring trace metal contamination introduced during processing, storage or refining
- Support for regulatory compliance where maximum metal limits apply
- Research and method development in food chemistry and lipid analysis
Practical notes: inject 20 µL sample aliquots for routine measurements; use an uncoated graphite tube for Cu and Ni determinations and a niobium-coated tube for Fe to ensure complete iron recovery. Preheat samples and standards (60 °C) before analysis to ensure reproducible transfer.
Related Standards
- ISO 661: Preparation of test sample (animal and vegetable fats and oils)
- ISO 5555: Sampling of animal and vegetable fats and oils
- ISO 3696: Water for analytical laboratory use
- ISO 5725: Precision of test methods (interlaboratory reproducibility and repeatability)
Practical value
EN ISO 8294:1999 provides a robust GFAAS workflow for trace-metal determination in fats and oils, including blanking, calibration and furnace tube treatment recommendations. Precision was established through an international IUPAC interlaboratory study (32 laboratories); repeatability and reproducibility limits are provided in the standard. Laboratories implementing this method benefit from a standardized approach that supports consistent, comparable results across testing facilities.
