Overview
ISO 20595:2018 - "Water quality - Determination of selected highly volatile organic compounds in water - Method using gas chromatography and mass spectrometry by static headspace technique (HS‑GC‑MS)" - specifies a standardized laboratory method for measuring selected highly volatile organic compounds (VOCs) in water. The method targets volatile halogenated hydrocarbons and gasoline-related components (e.g., BTXE, TAME, MTBE, ETBE) in drinking water, groundwater, surface water and treated wastewater at mass concentrations greater than 0.1 µg/L (lower limits depend on the analyte, blank values and matrix).
Key topics and technical requirements
- Analytical principle: Static headspace sampling - a measured water volume is sealed in a headspace vial, heated to equilibrium, and a defined gas aliquot from the headspace is analyzed by gas chromatography with mass spectrometric detection (HS‑GC‑MS).
- Scope of compounds: A comprehensive list of determinable VOCs is provided (see Table 1 in the standard), including many chlorinated solvents, aromatics (benzene, toluene, xylenes), and oxygenates (MTBE, ETBE, TAME).
- Performance and sensitivity: Applicable for concentrations >0.1 µg/L; actual lower reporting limits vary by compound, matrix and blank levels.
- Quality control:
- Regular blank value control to avoid laboratory air and solvent contamination.
- Control over the total procedure (internal standards, calibration).
- Identification rules using mass spectra and retention data.
- Matrix and interferences:
- Matrix effects can alter response factors; salt addition (sodium chloride or sodium sulfate) is recommended to improve sensitivity but may introduce interferences.
- Some compounds can decompose during headspace heating (example: 1,1,2,2‑tetrachloroethane → trichloroethene), potentially causing false positives.
- Supporting content: Guidance on reagents, apparatus, sampling, GC‑MS operating conditions, calibration (including internal standards), evaluation, reporting and example conditions are supplied in informative annexes. Performance data and limitations are provided.
Applications and users
- Who uses it: Environmental testing laboratories, water utilities, regulatory agencies, contract analytical labs, environmental consultants and researchers.
- Use cases:
- Routine monitoring of drinking water and groundwater for VOC contamination.
- Compliance testing for environmental regulations and remediation monitoring.
- Investigations of fuel‑related contamination and industrial solvent releases.
Related standards and references
- Normative sampling and laboratory references cited include ISO 3696 (laboratory water) and the ISO 5667 series (sampling of waters: preservation, groundwater, surface water, wastewater, drinking water).
- Annexes in ISO 20595:2018 provide example GC columns, headspace vials, septa, internal standards and typical headspace/GC conditions.
Note: ISO 20595:2018 requires trained laboratory personnel and adherence to normal safety and QA practices.