Intercomparison 0317: pH, Cond, HCO3, NO3+NO2 C1, SO4, Ca, Mg, Na, K, Fe, Mn, Cd, Pb, Cu, Ni and Zn (ICP Waters report 74/2003)

Abstract

75 laboratories received samples for the intercomparison 0317, and 69 laboratories in 27 countries submitted results. Two sample sets were used, one for the determination of major ions, and one for heavy metals. Based on the general target accuracy of ± 20 %, 71 % of the overall results were considered acceptable. The best results were reported for the analytical variables sodium, sulfate and copper, with a percentage of acceptable results of 92, 83 and 83 %, respectively. Lowest percentage of acceptable results were observed for manganese, lead, and iron. Common for these analytical variables is their low concentrations being rather close to their detection limits. For pH and alkalinity only 57 % and 58 % of the result pairs, respectively, were acceptable based on a target accuracy of ± 0.2 units. Harmonization of the analytical methods used is necessary to improve the comparability for pH.