SIM.QM-S17 Ethanol in Aqueous Matrix: Supplement Key Comparison, Model 1

Main text To establish international measurement capabilities for the determination of ethanol in aqueous matrices, the CCQM Organic Analysis Working Group (OAWG) has performed three ethanol Key comparisons (2002: CCQM-K27a for forensic aqueous ethanol and CCQM-K27b for ethanol in wine as a commodity; 2005: CCQM-K27 subsequent studies - four levels of ethanol in water; 2007: CCQM-K27.2 Subsequent 2 for forensic levels). To provide an opportunity for the NMIs and DIs within the RMOs, three Key comparisons has been conducted within SIM (SIM.QM-K1, SIM.QM-K27) and AFRIMETS (AFRIMETS.QM-K27). In addition, for the NMIs to support their ethanol in aqueous matrices measurements capabilities, a Track A Model 2 (formerly known as Track B) Key comparison CCQM-K79 (2010) has been completed to compare aqueous ethanol certified reference material (CRM) solutions certified by the participant NMIs and DIs. The current comparison is important to NMIs and DIs to maintain their ethanol in water measurement capabilities, to claim it as a new one as well as to complement their existing measurement capabilities, mainly within the range where the alcohol meter (breathalyzer) needs to be calibrated and verified. In 2017, several NMIs and DIs in SIM expressed their interest in a complementary SIM.QM-K27 comparison, therefore CENAM and INMETRO agreed to collaborate for the realization of a SIM supplement comparison, which was identified as SIM.QM-K27.2019 by the OAWG, and the final assigned name by SIM was SIM.QM-S17. The main purpose of this comparison was to offer to SIM countries and other regions an additional opportunity for the NMI and DIs to evaluate their measurements capabilities in determining mass fraction of ethanol in an aqueous matrix within the mass fraction range from 0.1 mg/g to 5 mg/g. Fourteen laboratories were registered to take part in this comparison, and thirteen sent their results. This report presents the results of the SIM Key comparison SIM.QM-S17. The measurements capabilities demonstrated by the participants in SIM.QM-S17, underpin their ability to assign reference values of ethanol content in aqueous samples for both forensic and commodities applications. Successful participation in SIM.QM-S17 demonstrates the laboratories measurement capabilities in determining mass fraction of ethanol in an aqueous matrix within the mass fraction range from 0.1 mg/g to 5 mg/g. The study material was two batches of solutions of ethanol in water prepared gravimetrically at concentrations between 0.1 mg/g - 5 mg/g by CENAM, dispensed in glass bottles of 50 mL sealed with tear off aluminum crimp seals, with rubber stoppers. In previous SIM.QM.K27 comparison, the purity-corrected gravimetric value of the aqueous ethanol solutions assigned by the coordinating NMI was used to link SIM.QM-K27 to the CCQM-K27 Key comparison reference value (KCRV), where 1 % uncertainty was assigned to the KCRV to have the same uncertainty from the CCQM-K27.2. For this comparison, SIM.QM-S17 two levels aqueous ethanol solutions, the purity assigned by CENAM was not used for KCRV as was informed initially in the protocol, instead in 5-June-2020 at the OAWG, CENAM gravimetric values were presented, as well as the participants results evaluated by four different statistical approaches to assess the candidate KCRV. For both levels of ethanol in aqueous matrix solutions, the DerSimonian-Laird Weighted mean and the Hierarchical Bayes mean methods seem to give a better estimation of the KCRV ± KCRU95 candidate and was agreed by OAWG to use the Hierarchical Bayesian mean, from where the KCRV for SIM.QM-S17 Level 1 (Low-level) and Level 2 (high-level) were (240.92 ± 1.28) mg/kg (k =2) and (389.87 ± 1.52) mg/kg (k =2), respectively. All the thirteen participants in the SIM.QM-S17, including both coordinators, demonstrated their capability to measure ethanol in aqueous matrix in the mass fraction range of 0.1 mg/g to 5 mg/g. 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).