Results of CCQM-K99 key comparison on unknown phosphate buffer pH ∼ 7.5 at 5 °C, 15 °C, 25 °C, 37 °C and 50 °C are reported. Good agreement is found between the majority of participants. 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 (CIPM MRA).

The subsequent key comparison CCQM-K19.1 has been carried out in 2010 as a follow-up comparison to CCQM-K19. Three laboratories (NMIJ, PTB and SMU) took part in both comparisons. Their results are consistent. The assigned uncertainties are reliable and in the same order. These results provide the link to CCQM-K19.As well as the original comparison the subsequent key comparison was organised to demonstrate the capability of the interested National Metrology Institutes to measure the pH value of an unknown borate buffer by a primary method at 15 degrees C, 25 degrees C and 37 degrees C. Eight laboratories took part in CCQM-K19.1. The participants either were not able to participate in the original comparison or participate only in the Pilot Study CCQM-P82 running in parallel to CCQM-K19. In one case the laboratory expressed doubts on the integrity of the sample provided in CCQM-K19.The result in CCQM-K19.1 is the acidity function at zero chloride molality, AF(0) of the unknown borate buffer solution.Most participants in the key comparison CCQM-K19.1 demonstrated improved capabilities. This especially applies for the laboratories original taken part in the pilot study CCQM-P82. In some cases previous results could be confirmed. The hidden reasons for that have still to be clarified.

The subsequent key comparison CCQM-K18.1 was started in order to evaluate the equivalence of metrology institutes as a follow-up to the previous key comparison CCQM-K18 for institutes that could not take part in the comparison at that time or did not consider their results representative of their capabilities. A carbonate buffer of a slightly different composition to that in CCQM-K18 was used.There were seven institutes plus the coordinating laboratory participating in this subsequent comparison. Most of the participating institutes showed significant improvement; in some cases the new results confirmed the previous ones. The reasons for this have still to be elucidated.

Coulometry is a primary method for measuring the amount of substance of high-purity compounds and its solutions. Coulometric titration is used to determine the purity of primary reference materials for acid/base, precipitation, redox and complexometric titrations. This work aims at presenting the primary system of coulometry from Inmetro, which was used for the characterization of hydrochloric acid solutions from nominal values of 1.0 mol·kg− 1 and 0.01 mol·kg− 1 , as well as the preliminary studies and the results of the key comparison CCQM-K48, which Inmetro has recently participated to determine the purity of potassium chloride (KCl).The reference materials characterized by the Inmetro's primary system of coulometry will be used to guarantee the traceability and reliability to the measurement results from titrimetric analysis carried out by the Brazilian chemical analysis laboratories.

National Institute of Metrology, Standardization and Industrial Quality, Inmetro from Brazil, established the primary system of electrolytic conductivity in 2007. The objective of this work is to present the traceability chain of electrolytic conductivity measurements and the use of primary system in the certification of reference materials, which are used for calibration of conductivity meter. The correct measurement of the electrolytic conductivity using certified reference materials to obtain reliability in the results is extremely relevant for the purity of water, health, environment and chemical processes. In 2007, Inmetro participated in a key-comparison, CCQM-K36.1, with this primary system in order to check its performance on different values of electrolytic conductivity.

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).