NIST: new reference material SRM 1947a made from Lake Ontario trout tissue — certified mercury, PCBs, organochlorine pesticides and PBDEs, PFAS as non-certified values
On 28 April 2026 the US NIST described the reference material SRM 1947a Great Lakes Fish Tissue, the successor to the sold-out SRM 1946 and SRM 1947. It helps laboratories monitoring contaminants in fish validate methods and control quality.
- The material was prepared from twice-cryomilled Lake Ontario trout. A unit is four jars of about 10 g (wet mass) each of frozen homogenate; the certificate was issued on 9 December 2025, and on 12 May 2026 the unit for total mercury was corrected from mg/kg to µg/kg.
- Certified values (wet-mass basis, expanded uncertainty with k = 2) cover total mercury at 174.9 ± 3.1 µg/kg, 16 PCB congeners, 5 organochlorine pesticides (e.g. 4,4′-DDE 221 ± 5 µg/kg) and 4 PBDE congeners, all metrologically traceable to the SI. PFAS, including PFOS at 12.9 ± 2.0 µg/kg, are given in an appendix as non-certified values — useful for method development but without SI traceability.
- The material must be stored at −80 °C or lower and must not thaw before subsampling. Certified values apply to test portions of at least 0.25 g for mercury and at least 2.5 g for PCBs, pesticides and PBDEs; they are valid until 31 July 2040.
- NIST notes that US state and federal laboratories monitor fish for mercury, PFAS, PCBs and DDT, among others, and that the material lets them confirm method accuracy at low levels in a real matrix. Certification details are documented in NIST SP 260-260.
Source: NIST — SRM Story: SRM 1947a Great Lakes Fish Tissue (28.04.2026)