Overview
ISO 7359:1985 - Essential oils - Analysis by gas chromatography on packed columns - General method - defines a general, repeatable procedure for chromatographic analysis of essential oils using packed GC columns. The standard covers recurrent parameters, apparatus, reagents, test mixtures, column performance checks, retention-index determination and quantitative measurement by peak-area evaluation. It is intended for routine identification of constituents (by retention index) and for quantitative determinations using internal standards.
Key topics and technical requirements
- Scope & principle: Analysis of small samples of essential oils by gas chromatography on packed columns to obtain characteristic profiles and determine specific constituents.
- Reagents and gases: Specifies use of high‑purity carrier gases (hydrogen, helium or nitrogen) and auxiliary detector gases; recommends using freshly distilled, analytical‑grade reagents.
- Reference and test substances: e.g., linalyl acetate (≥98%) for column inertness, linalol (≥99%) and methane (≥99%) to check column efficiency, and normal alkanes (≥95%) for retention‑index work.
- Test mixture: Typical control mixture includes limonene, acetophenone, linalol, linalyl acetate, naphthalene and cinnamic alcohol to evaluate separation and polarity behaviour.
- Column specifications: Packed columns of inert material (glass or stainless steel), 2–4 mm ID and preferably 2–4 m length; supports must be inert (e.g., silanized celite).
- Column performance checks:
- Chemical inertness: single peak for linalyl acetate under test conditions.
- Efficiency: evaluate number of theoretical plates N from linalol at 130 °C (N ≥ 3 000).
- Resolution/Separation: defined methods to calculate resolution and percent separation (standard criteria such as ≥95% for specified peak pairs).
- Retention index determination: Procedures for isothermal and temperature‑programmed runs using normal alkanes; retention indexes used for constituent identification.
- Quantification methods: Internal standard and internal normalization approaches; the standard provides formulae for response factors and calculation of constituent content from peak areas and weighed reference materials.
- References: Cross‑references ISO 356 (sample preparation) and ISO 7609 (capillary‑column method).
Applications and users
ISO 7359:1985 is used by:
- Analytical chemists in fragrance, flavor and aromatherapy industries
- Quality control laboratories verifying essential oil composition and purity
- Regulatory and standards bodies requiring harmonized test methods
- R&D teams characterizing essential‑oil profiles and comparing column packings
Practical applications include routine quality control, identity verification (via retention index), troubleshooting column performance, and comparative analysis of essential‑oil batches.
Related standards
- ISO 356 - Essential oils - Preparation of test sample
- ISO 7609 - Essential oils - Gas chromatography on capillary columns (general method)
Keywords: ISO 7359:1985, essential oils, gas chromatography, packed columns, retention index, internal standard, column efficiency, chromatographic analysis.