CCQM-K91.2022 key comparison on pH of an unknown phthalate buffer

Abstract

Main text Key comparison CCQM-K91.2022, a repetition of the previous comparison CCQM-K91 from 2011, was performed to evaluate the degree of equivalence between pH measurement results of an unknown phthalate buffer reported by participating National Metrology Institutes (NMIs) and Designated Institutes (DIs). The participants used the highest-level metrological method existing at their institution. The nominal pH value of the buffer was 4.0 at 25 °C and the suggested measurement temperatures were 5 °C, 15 °C, 25 °C, 37 °C, and 50 °C. There was a good agreement among the results from most participants at 15 °C, 25 °C, and 37 °C. Due to the lack of results, no evaluation was possible of results at 5 °C and 50 °C. 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).