Determination of the purity of acidimetric standards by constant-current coulometry, and the intercomparison between CRMs

The accuracy and uncertainty of the coulometric measurement results of reference materials for acidimetric titration were examined in this study. The results for amidosulfuric acid and potassium hydrogen phthalate are presented. The uncertainty was investigated by examining the dependency on the sample size and on the electrolysis current. Changes in the titration parameters did not result in any significant effects on the titration results. Acidimetric standards with the certified value linked to the SI were developed. In addition, the intercomparison of acidimetric standards was carried out by gravimetric titration, and the relationship between our coulometric results was determined. Furthermore, due to recent internationalization, not only the traceability to the SI but also the relationship and consistency of their analytical data have gained increasing importance. Our results were validated using certified reference materials (CRMs) obtained from different National Metrology Institutes (NMIs), and their relationships are presented.