ISO 20179:2005

Overview

ISO 20179:2005 specifies a laboratory method for the determination and quantification of microcystins in raw water (containing cyanobacterial biomass) and treated water (e.g., tap water). The method combines solid phase extraction (SPE) for sample enrichment and cleanup with reversed‑phase high performance liquid chromatography (RP‑HPLC) and UV/diode‑array detection (238 nm) for quantification. It is validated for MCYST‑LR, MCYST‑YR and MCYST‑RR and can be applied to related structural variants (though unambiguous identification may be limited by co‑elution and lack of standards). The standard supports following the World Health Organization guidance value (1 µg/L MCYST‑LR) after SPE enrichment.

Safety note: Microcystins are highly hepatotoxic. ISO 20179 warns that laboratory wastes must be handled and disposed of as highly toxic chemical waste and recommends appropriate safety procedures.

Key Topics and Requirements

• Scope: Analysis of microcystins in raw and treated waters; validated for MCYST‑LR, ‑YR, ‑RR.
• Principle: Filter biomass, solvent extraction (methanol/water), SPE clean‑up, SPE elution (methanol/water 90:10 + 0.1% TFA), RP‑HPLC-UV at 238 nm.
• Reagents & standards: HPLC‑grade methanol, acetonitrile, trifluoroacetic acid (TFA); preparation and spectrophotometric verification of microcystin stock solutions (use of molar absorptivity and molar mass data provided).
• SPE performance: Cartridges must retain ≥100 µg analyte capacity and deliver recoveries of ≥80% for MCYST‑LR and ≥70% for MCYST‑RR/‑YR under specified test conditions. Cartridge material/brand affects recovery.
• HPLC system requirements: C‑18 type column (e.g., 250 mm length, 2–4.6 mm ID, 3–5 µm particles), column oven at ~35 °C, flow 0.3–1.0 mL/min, injection 5–20 µL, PDA/UV detector (200–300 nm). System LOD ≤ 0.1 ng/µL and LOQ ≤ 0.2 ng/µL (signal‑to‑noise criteria).
• Quality control: Preparation of mixed standards, spiking solution (1 µg/L) for method control, and performance data (precision, typical chromatograms, and optional MS detection in informative annex).

Applications and Users

ISO 20179 is intended for:

• Municipal and private drinking water laboratories monitoring cyanotoxins.
• Environmental monitoring of lakes, reservoirs and raw water sources.
• Public health agencies assessing compliance with WHO guidance and local regulations.
• Research laboratories developing or comparing microcystin occurrence data.
• Water utilities conducting routine or investigative testing after algal bloom events.

Practical applications include routine screening, method validation, and supporting regulatory compliance decisions where reliable quantification of MCYST‑LR, ‑YR and ‑RR is required.

Related Standards

• ISO 3696:1987 - Water for analytical laboratory use (quality of reagents/water).
• ISO 5667‑4 and ISO 5667‑5 - Guidance on sampling from lakes and drinking water sampling.
• ISO 20179 Annex A - Mass spectrometry (MS) as alternative detection (informative).

Keywords: ISO 20179, microcystins, SPE, HPLC‑UV, water quality testing, cyanotoxins, MCYST‑LR, MCYST‑YR, MCYST‑RR.