CCQM K27 (a, b): Determination of ethanol in aqueous matrix

A key comparison on the determination of ethanol in aqueous matrix has been successfully completed. Nine national metrology institutes (NMIs) participated in this key comparison and used the techniques of gas chromatography with flame ionization detection (GC-FID), isotope dilution gas chromatography-mass spectrometry (GC-IDMS), gas chromatography-combustion-isotope ratio mass spectrometry (ID-GC-C-IRMS) and headspace-GC-FID for the determinations. Three samples were distributed to participants. Two of these samples (Samples A and B) were aqueous solutions that had been spiked gravimetrically with ethanol (at mass fractions of ethanol representing forensic standards, CCQM-K27a), the other (Sample C) was a commercial (red) wine (representing a traded commodity, CCQM-K27b). The KCRV for Sample A is 0.8040 - 0.0080 mg g-1, that of Sample B is 120.90 - 0.35 mg g-1 and that of Sample C is 81.23 - 0.24 mg g-1 of ethanol in the appropriate aqueous matrix. These results are an improvement over those of the corresponding pilot study (CCQM-P35). The RSD for Sample A is 1.5% compared to 2.3% for a similar mass fraction for the pilot study. For the wine sample (Sample C) corresponding RSDs are 0.44% for this key comparison and 2.3% for the pilot study. This demonstration of capability will enable forensic ethanol standards to be compared across national boundaries. Likewise the ability to measure the typical mass fraction of ethanol found in wine is important since such commodities are traded worldwide and are liable to varying levels of excise duty. Thus this successful key comparison has demonstrated a broad range of capability by NMIs for the measurement of ethanol for both forensic and excise purposes.