Overview
ISO 11349:2010 - Water quality - Determination of low‑volatility lipophilic substances - Gravimetric method describes a standardized laboratory procedure to quantify low‑volatility lipophilic substances in water by gravimetry. The method covers dissolved, emulsified or suspended lipophilic materials (e.g., animal/vegetable oils, mineral oils, waxes, greases and some non‑ionic surfactants) in the concentration range of about 10 mg/L to 500 mg/L. It is applicable to all kinds of water but not suitable for samples with a separate oil layer.
Key topics and requirements
- Principle: liquid–liquid extraction with a non‑polar hydrocarbon, evaporation/concentration of the extract and gravimetric determination after drying.
- Scope limits: intended for low‑volatility substances (boiling point > 250 °C); concentration range ~10–500 mg/L (dilute samples above this range).
- Reagents: non‑polar hydrocarbons with boiling range 36–69 °C (e.g., petroleum ether 40–60 °C, n‑hexane), anhydrous Na2SO4, MgSO4·7H2O, mineral acid (e.g., H2SO4, 2 mol/L), acetone and high‑purity water (ISO 3696 grade).
- Sample handling: acidify to pH ≤2 for preservation if not analyzed immediately; store at ≈4 °C and analyze within 7 days.
- Procedure highlights:
- Homogenize sample, extract (typically two 50 mL solvent portions), combine organic phases, dry over sodium sulfate, filter through a hydrophobic filter.
- Concentrate extract (e.g., rotary evaporator), strip solvent, dry at 80 ± 3 °C for 15 min, cool in desiccator and weigh.
- Quality control:
- Blank determinations carried out routinely - blank must not exceed 3 mg/L.
- Recovery check using a vegetable oil spike (e.g., olive oil) - required recovery 90–105%.
- Reporting: mass concentration in mg/L to two significant figures; test report must reference ISO 11349:2010 and include sampling, pretreatment and any deviations.
Applications and users
ISO 11349:2010 is used by:
- Environmental and regulatory monitoring laboratories assessing oil and grease, fats and other lipophilic contaminants in surface water, industrial and municipal effluents.
- Wastewater treatment facilities and industrial process control labs for compliance and performance monitoring.
- Consultants and accredited testing bodies requiring a traceable, reproducible gravimetric method for low‑volatility lipophilic substances.
Practical benefits include a simple, well‑documented gravimetric workflow, suitability for a wide range of water matrices, and clear QC criteria for routine monitoring.
Related standards
- ISO 3696 - Water for analytical laboratory use (quality of water used in the method)
- ISO 4788 - Laboratory glassware (measuring cylinders)
- ISO 5725‑2 - Precision (repeatability and reproducibility) of measurement methods
Keywords: ISO 11349:2010, water quality, gravimetric method, low‑volatility lipophilic substances, oil and grease, extraction, petroleum ether, n‑hexane, laboratory method.