The certification of 202Hg enriched methyl mercury amount content and isotopic composition Hg as methyl mercury in ethanol/water solution : ERM-AE671

This report describes the production of ERM®-AE671, a 2 % ethanol/water material certified for the amount content of isotopically enriched methyl mercury (CH3(202Hg)) and certified for the isotopic composition of Hg present as methyl mercury (CH3Hg+). The material was produced following ISO Guide 34:2009. Twenty two ampoules of ERM-AE670 containing isotopically enriched methyl mercury chloride (CH3(202Hg)Cl) in 2 % ethanol/water solution were used as starting material. Each ampoule contained approximately 5 g of solution. The content of ERM-AE670 ampoules was gravimetrically diluted with 2 % ethanol/water solution to create enough material for 220 new units. The diluted CH3(202Hg)Cl solution was filled into quartz ampoules which were flame sealed. Between-unit homogeneity was quantified and stability during dispatch and storage were assessed in accordance with ISO Guide 35:2006. The certified value was obtained from the gravimetric preparations, taking into account the amount of content and isotopic composition of the base material. The certified values were confirmed by isotope dilution mass spectrometry as independent verification method measurements within the scope of accreditation to ISO/IEC 17025:2005. Uncertainties of the certified values were calculated in compliance with the Guide to the Expression of Uncertainty in Measurement (GUM) and include uncertainties related to possible inhomogeneity, instability and characterisation. The main purpose of the material is to be used as spike isotopic reference material for determination of CH3Hg content in an unknown samples by species-specific isotope dilution through a measurement of the mercury isotope amount ratio R(B) = n(200Hg)/n(202Hg) of CH3Hg, in a blend. The CRM is available in quartz glass ampoules containing 5 g of liquid species solution flame sealed under nitrogen atmosphere. The CRM was accepted as European Reference Material (ERM®) after peer evaluation by the partners of the European Reference Materials consortium.