Overview - ISO 20596-1:2018 (Water quality, cVMS by purge and trap GC‑MS)
ISO 20596-1:2018 specifies a validated analytical method for the quantitative determination of cyclic volatile methylsiloxanes (cVMS) in non‑filtered water samples using purge and trap extraction combined with isotope dilution gas chromatography–mass spectrometry (GC‑MS). Target analytes are D4 (octamethylcyclotetrasiloxane), D5 (decamethylcyclopentasiloxane) and D6 (dodecamethylcyclohexasiloxane). The method is suitable for surface water, ground water and wastewater, with an analytical range typically from 0.01 µg/L to 1 µg/L per compound (and up to 1–100 µg/L after dilution or sample adjustment, depending on matrix).
Key topics and technical requirements
- Principle: purge and trap extraction of analytes from whole water samples, solvent elution, and determination by GC‑MS with isotope dilution internal standards.
- Analytes: D4, D5, D6 (CAS numbers included in the standard).
- Sampling & contamination control: use silicone‑free containers and consumables; rinse containers with acetone and n‑hexane; avoid personal care products and other sources of silicone contamination during sampling and analysis.
- Sorbent & purge system: styrene–divinylbenzene polymer sorbent recommended; purge and trap assemblies and sorbent conditioning described.
- Reagents & gases: grade‑1 water, acetone, n‑hexane, anhydrous sodium sulfate; nitrogen (≥ 99.996 % v/v) for purging and drying.
- Standards & calibration: prepare multi‑point calibration (at least five levels) with isotope‑labelled internal standards; storage of standards below −18 °C and regular blank checks.
- Quality control: blanks, identification criteria, calibration validation, and treatment of out‑of‑range results; performance data and example chromatograms are provided in annexes.
- Safety & competence: tests must be carried out by suitably qualified personnel and follow normal laboratory safety practice.
Applications and who uses this standard
- Environmental laboratories performing monitoring of water quality for regulatory compliance or research.
- Wastewater treatment plants and consultants assessing cVMS influent/effluent and environmental discharge.
- Manufacturers and suppliers of silicone‑containing products monitoring environmental emissions.
- Research institutions studying fate, transport and ecotoxicology of volatile siloxanes.
The method supports accurate, low‑level quantification of cVMS to inform risk assessments, regulatory reporting and pollution source tracking.
Related standards
Normative references include ISO 3696 (water for analytical use), ISO 5667 series (sampling guidance for lakes, rivers, groundwater, wastewater), ISO 8466‑1 (calibration/evaluation of analytical methods) and ISO 4793 (lab filters). Annexes in ISO 20596‑1 provide practical examples (sorbents, purge assemblies, columns, GC‑MS conditions and performance data).