Supplementary comparison study - measurement capabilities for the quantification of ethanol in water

Main text The accurate quantification of ethanol in water is essential for forensic applications such as blood and breath alcohol testing and for commercial applications such as the assessment of alcoholic beverages. The intercomparison EURAMET.QM-S14 is part of a capacity building project named ALCOREF "Certified forensic alcohol reference materials"[1] that is running within the European Metrology Programme for Innovation and Research (EMPIR) [2]. The intercomparison should allow project partners and other interested National Metrology Institutes (NMIs) and Designated Institutes (DIs) to benchmark their analytical methods for the quantification of ethanol in water. The study plan was agreed by the European Association of National Metrology Institutes (EURAMET) Subcommittee Bio- and Organic Analysis (SCBOA) and the Organic Analysis Working Group (OAWG) of the Comité Consultatif pour la Quantité de Matière (CCQM) in February and April 2019, respectively. The intercomparison was coordinated by BAM. Two concentration levels relevant for the calibration and verification of evidential breath alcohol analysers were distributed to study participants. Fifteen institutes from 15 countries registered for the intercomparison and returned results. Participants mostly applied gas chromatography with flame ionisation detection (GC-FID) or mass spectroscopy (GC-MS), one participant used titrimetry and one participant employed a test bench for breath analyser calibration ("bubble train"). Participants did either in-house purity assessment of their commercial ethanol calibrants by Karl-Fischer titration, chromatographic methods, quantitative nuclear magnetic resonance spectroscopy (qNMR) and/or density measurements; or they used ethanol/water Certified Reference Materials (CRMs) from NMIs/DIs for calibration. CCQM OAWG agreed to use a consensus value from participants' results that utilizes the reported uncertainties as Key Comparison Reference Value (KCRV). The Gaussian Random effects model with Hierarchical Bayesian solution (HB-REM) is a reasonable approach in this case. The KCRVs and Degrees of Equivalence (DoEs) were calculated with the NIST consensus builder version 1.2 Hierarchical Bayes procedure [3]. Successful participation in the interlaboratory comparison has demonstrated the capabilities in determining the mass fraction of ethanol in aqueous matrices in the range 0.1 mg/g to 8 mg/g. Fourteen out of 15 participants have successfully quantified both samples, one participant successfully quantified only the lower-level (0.6 mg/g) sample. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).