Final report of key comparison CCQM-K18: pH of carbonate buffer

The key comparison CCQM-K18 was started in order to evaluate the equivalence of metrology institutes as a follow-up of the previous study CCQM-P52. As a sample a carbonate buffer solution was used with a composition slightly different to the usual one. There were 13 institutes participating in the comparison using a primary method for pH measurement. The fair agreement between the results reflects increased difficulty in measurement, where the buffer composition may slightly change during the measurement and extrapolation to the start time of measurement is usually necessary. Main text. 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 kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).