Overview
ISO 22972:2004 defines a general method for analysing essential oils by gas chromatography (GC) on chiral capillary columns to determine the enantiomeric excess (EE) or enantiomeric distribution of chiral constituents. It establishes the analytical principle, required apparatus and reagents, column performance criteria, calculation formulas for EE and distribution, and reporting conventions for routine chiral GC of essential oils.
Key topics and technical requirements
- Analytical principle: GC separation on capillary columns whose inner walls are coated or impregnated with a chiral stationary phase to resolve enantiomers; identification by reference substances and, if needed, retention indices.
- Column specifications: inert capillary columns with inner diameter ≤ 0.53 mm and length 10–60 m; common chiral phases include substituted β‑cyclodextrins.
- Column performance: efficiency measured on the less‑retained enantiomer with a minimum of 25 000 theoretical plates (note: lower efficacy allowed for some 2D setups); resolution and separation assessed per ISO 7609.
- Gases and detectors: carrier gases-hydrogen, helium or nitrogen; detector supply gases per detector (e.g., air + hydrogen for FID, helium for MS). Injection and detector temperatures must be independently controlled.
- Sample preparation: follow ISO 356; may include selective transfer (e.g., trapping or 2D-GC) or derivatization where specified for particular oils.
- Quantification and formulas: ISO 22972 provides formulas to calculate enantiomeric excess (E) from peak areas and to express enantiomeric distribution as % (R)/(S). Special attention is recommended when EE > 95% or distribution > 97.5% to avoid integration errors for trace enantiomers.
- Quality checks: verify absence of co‑elution (mass spectrometry recommended) and determine retention indexes when required.
- Reporting: test report content follows the general clauses of ISO 7609.
Applications and users
- Who uses it: analytical chemists, quality control and R&D laboratories in fragrance, flavor, pharmaceutical, and natural products industries; regulatory bodies and standards organizations performing compositional and authenticity testing of essential oils.
- Practical uses:
- Determining chiral purity and enantiomer ratios in essential oils for quality control and specification.
- Detecting adulteration or origin/authenticity markers based on enantiomeric profiles.
- Method transfer and validation for laboratories implementing chiral GC analyses.
Related standards
- ISO 7609:1985 - Essential oils - Analysis by gas chromatography on capillary columns - General method (referenced for general clauses, retention index and calculation methods)
- ISO 356 - Essential oils - Preparation of test samples (sample handling and preparation procedures)
Keywords: ISO 22972:2004, essential oils, gas chromatography, chiral capillary columns, enantiomeric excess, enantiomeric distribution, chiral analysis, enantiomers, cyclodextrin stationary phase.