Key comparison CCQM-K148.b - polar analyte in solid organic material: mass fraction of oxytetracycline

Main text The CCQM-K148.b comparison, undertaken with a parallel pilot study CCQM-P187.b, was coordinated by the BIPM and UME on behalf of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM) Working Group on Organic Analysis (OAWG). It was undertaken for National Measurement Institutes (NMIs) and Designated Institutes (DIs) which provide measurement services in organic analysis under the CIPM Mutual Recognition Arrangement (MRA) and was designated a Track A comparison within the OAWG implementation of the CCQM Strategy for Programme Development 2021-2030.1. The ability to assign the mass fraction content of the primary component in a solid organic material that an NMI makes available as a pure substance Reference Material or that is used by an NMI in-house as a Primary Reference Material is a critical technical competency for the provision of SI-traceable quantitative measurement results in organic analysis. The purity property value assigned to the Primary Reference Material in a measurement hierarchy anchors the calibration chain for all results linked to that material. Participation in the series of Track A purity comparisons organized by the OAWG allows an NMI/DI to demonstrate that their procedure for the assignment of a purity property value and its associated uncertainty are fit for purpose for their intended application. Evidence of successful participation in formal, relevant international comparisons is required under the CIPM Mutual Recognition Arrangement (MRA) to support calibration and measurement capability (CMC) claims made by NMIs and DIs. Nineteen NMIs in addition to the BIPM, submitted results in CCQM-K148.b (one laboratory submitted results to the pilot study). Participants were required to assign the mass fraction of oxytetracycline free base (OTC), standardized to the value expected at 50% relative humidity, present in a solid material containing the oxytetracycline hydrochloride salt as the principal component. Eight participants assigned their final value for the comparison through the combination of values obtained by independent mass balance and qNMR methods. Seven participants reported a result from a mass balance method only and five reported a result by qNMR only. Successful participation in CCQM-K148.b demonstrates capabilities for assigning the mass fraction of organic compounds with molar mass in the range of 75 g/mol to 500 g/mol, having high polarity (pKow > -2), including compounds presenting significant hygroscopicity, in an organic solid material. 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).