Abstract. In the CCQM-P32 pilot study two gravimetrically prepared anion calibration solutions of chloride and phosphate each of about 1 g/kg mass fraction were investigated. The comparison was an activity of the Inorganic Analysis Working Group of CCQM in 2002 and was piloted by the Swiss Federal Laboratories for Materials Testing and Research (EMPA).

The following institutes participated in this study (in alphabetical order): BAM (Germany), CENAM (Mexico), EMPA (Switzerland), GUM (Poland), KRISS (South Korea), LNE (France), NIST (United States of America), NMIJ (Japan), NRCCRM (China), PTB (Germany), SMU (Slovakia).

For the chloride calibration solution 11 participants provided 16 results by the following analytical techniques: coulometry (7), titrimetry (5) and ion chromatography (4). The phosphate amount content was determined by 9 NMIs and 11 results were reported. Phosphate ion chromatography was the most applied technique (4), followed by titrimetry (2), ICP-OES (2), gravimetry (1) and ion-exchange coulometry (1). All results were found within a range of ±0.5% with respect to the gravimetric value. The variability (RSD) of the results is 0.13% for chloride and 0.26% for phosphate. The reported results of all participants are also graphically displayed in this report.

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The final report has been peer-reviewed and approved for publication by the CCQM Working Group on Inorganic Analysis, according to the provisions of the Mutual Recognition Arrangement (MRA).