Overview
ISO 22892:2006 - "Soil quality - Guidelines for the identification of target compounds by gas chromatography and mass spectrometry" provides harmonized criteria for identifying target compounds in soil (and other environmental) samples using GC‑MS. It is a guidance standard intended to be used alongside specific analytical methods for particular compounds. The standard defines how to combine relative retention time checks with electron ionization mass spectral interpretation (and, where needed, additional MS techniques) to classify a compound as identified, indicated, or absent.
Key topics and technical requirements
-
Instrument mode and basic settings
- Ionization: Electron ionization (EI) (commonly 70 eV).
- Scan modes: Full scan and Selected Ion Monitoring (SIM) are allowed.
- Mass range: typically from m/z 35 up to the target’s highest mass + 10 u.
- Scan rate: recommended ≈10× peak frequency with a minimum of 7 scans per peak.
- Mass resolution: tune to nominal resolution with peak width at half-height ≤ 0.7 u.
-
Retention time criteria
- Use a retention time standard (often an internal standard) and calculate relative retention time; value shall be < 2.
- Peak maxima of extracted ion chromatograms are used for retention time decisions.
- Allowed difference between diagnostic ions’ retention times ≤ 20% of peak width at half-height (commonly ≈1 s).
-
Diagnostic ions and identification points
- Preferably select three diagnostic ions per target compound; intensities measured as peak height or area.
- Diagnostic ions must have S/N > 3 to count; lowest concentration for identification requires the weakest diagnostic ion to meet S/N > 3.
- Selection guidance: favor high m/z, even-mass fragments, molecular ion where possible, and isotope clusters (e.g., Cl-containing species).
- Identification is based on a point system: typically ≥3 identification points for a positive identification; 1–2 points yields an indication; none = absence (below detection limit).
- Additional identification points can be obtained from MS‑MS, chemical ionization, HR‑MS, chromatographic pattern, isotope dilution, spike/recovery, or corroborating analytical techniques.
-
Reporting and qualification
- The standard outlines a three‑step qualification process (GC criterion → analytical identification points → contextual/sample knowledge) and reporting categories (identified, indicated, absent).
- Annexes provide diagnostic ion tables, examples, and spectra to support implementation.
Practical applications
- Use in environmental laboratories for soil contamination screening, forensic investigations, and regulatory compliance testing.
- Integration with compound‑specific ISO or national methods to standardize compound identification, reduce false positives, and support defensible results.
- Helpful for method development, validation, QA/QC, and reporting of GC‑MS soil analyses.
- Environmental and analytical laboratories performing GC‑MS on soil samples
- Method developers and standard writers
- Quality managers and auditors applying ISO/IEC 17025 accreditation requirements
- Regulators and consultants evaluating contamination data
Related standards
- ISO/IEC 17025 (laboratory competence and quality assurance)
- Compound‑specific ISO and national standards for soil chemical determinations (used together with ISO 22892)
Keywords: ISO 22892, soil quality, GC‑MS, gas chromatography mass spectrometry, diagnostic ions, retention time, identification points, SIM, electron ionization, environmental analysis.
Open preview (PDF)Soil quality — Guidelines for the identification of target compounds by gas chromatography and mass spectrometry
