Overview
EN 16801:2016 (CEN) specifies a validated laboratory method for the determination of monomethylmercury (MMHg / methylmercury) in foodstuffs of marine origin. The method uses isotope dilution GC‑ICP‑MS (gas chromatography coupled to inductively coupled plasma mass spectrometry) and was validated in an interlaboratory study (ISO 5725‑2) on freeze‑dried tissues (mussel, squid, crab, dogfish liver, whale meat, cod, Greenland halibut) across mass fractions from 0.04 mg/kg to 3.6 mg/kg dry weight. Laboratory experience indicates the procedure is also applicable to fresh samples.
Key topics and technical requirements
- Analytical principle: Spike sample with an Hg‑isotope enriched MMHg standard, digest with tetramethylammonium hydroxide (TMAH), adjust pH, derivatise (sodium tetraethyl borate), extract into hexane, separate by GC, and quantify by ICP‑MS using isotope dilution calculation.
- Validation: Interlaboratory validation according to ISO 5725‑2; provides precision data for representative marine matrices.
- Reagents & quality:
- Ultra‑pure water (EN ISO 3696, grade 1) and high‑purity acids to minimize blanks.
- Recommended enriched MMHg spike standards and working dilutions (examples provided).
- Fresh preparation or controlled frozen storage of sodium tetraethyl borate solution.
- Instrumentation & performance:
- GC with heated transfer line and capillary column capable of resolving ethylmethylmercury.
- ICP‑MS capable of routine mass range 5–240 amu with adequate sensitivity and resolution.
- High‑purity argon/helium gases; optional xenon for tuning and oxygen to reduce carbon deposition.
- Sample handling: Typical test portion 0.2 g, spike weighing critical, digestion by TMAH with overnight dissolution if needed, centrifugation and hexane transfer before GC‑ICP‑MS analysis.
- Safety: The method involves hazardous chemicals and operations; users must follow appropriate laboratory safety and regulatory requirements.
Applications and users
- Food testing laboratories performing regulatory compliance testing of seafood for methylmercury.
- Regulatory agencies and public‑health authorities assessing seafood safety and exposure.
- Seafood industry quality control and supplier verification.
- Environmental and seafood research groups studying mercury speciation and bioaccumulation.
- Useful when accurate, isotope‑dilution quantification of MMHg is required across a range of marine tissues.
Related standards
- EN 13804 - General considerations for determination of elements and species in foodstuffs.
- EN ISO 3696 - Water for analytical laboratory use.
- ISO 5725‑2 - Reproducibility and repeatability (interlaboratory validation) - referenced for method validation.
Keywords: EN 16801:2016, methylmercury, monomethylmercury, isotope dilution, GC‑ICP‑MS, marine foodstuffs, TMAH, sodium tetraethyl borate, seafood testing, CEN.
