The intercomparison is part of the EMPIR 16RPT02 ALCOREF Project 'Certified forensic alcohol reference materials' which aims to develop certified ethanol in water reference materials for the calibration of evidential breath alcohol analysers.
Besides the ALCOREF institutes, other NMIs/DIs that deliver measurement services for forensic alcohol in water reference materials are invited to participate.
The comparison will allow NMIs/DIs to demonstrate their measurement capabilities for the quantification of ethanol in water in the mass fraction range 0.1 mg/g to 5 mg/g.
List of participating partners is not yet complete. More EURAMET and CCQM OAWG institutes will be invited.
Progress Report 2021-04-21
Study results were presented at the EURAMET SCBOA meetings in Feb 2020 and Feb 2021 and at the CCQM OAWG meeting in May 2020. Possible options for the key comparison reference values (KCRVs) were discussed: the gravimetric value and a consensus value from participants’ results. At the CCQM OAWG meeting it was decided to use a consensus value. The DerSimonian-Laird (DSL) mean and the Gaussian Random effects model (REM) with Hierarchical Bayesian (HB) solution were considered as reasonable approaches. The DSL and HB values agree well with each other and with the gravimetric value. The absolute Degrees of Equivalence (DoEs) for the participants were finally determined as the difference between the measured value and the HB consensus KCRV. Using a Monte Carlo technique, the DoEs and their uncertainties at the 95 % level of confidence were estimated along with the KCRV with the NIST consensus builder.
With a few exceptions, the DoEs confirm that the analytical methods of study participants for the quantification of ethanol in water are equivalent.
A Draft A report was prepared and submitted for review to EURAMET SCBOA and to the CCQM OAWG chair in March 2021.
Progress Report 2020-03-11
The study protocol was officially approved by CCQM OAWG, and the comparison was registered as key comparison EURAMET.QM-S14 in the BIPM key comparison database. A formal call for participation was released in August 2019 by CCQM-OAWG.
Two samples with different ethanol concentrations were prepared by the coordinating laboratory. They were assessed for homogeneity, short- and long-term stability and shipped in duplicate to the study participants in Sept 2019. In total 80 bottles of 1 L volume were distributed.
Measurements were performed in the participating laboratories using their in-house procedures for the quantification of ethanol in water. Most participants used gas chromatography with different detection modes (FID or MS) and injection modes (headspace, cool on column or split/splitless). Other laboratories used titrimetry, density measurements or a wet gas simulator coupled to a breath analyser.
All participants returned results, uncertainty budgets and method descriptions to the coordinating laboratory in Nov 2019. A first summary report was prepared and distributed for discussion among the study participants. Study results and possible options for the key comparison reference values were discussed at the EURAMET TC-MC SCOA meeting in February 2020.