Intercomparison 0620: pH, Cond, HCO3, NO3+NO2, Cl, SO4, Ca, Mg, Na, K, Fe, Mn, Cd, Pb, Cu, Ni and Zn (ICP Waters report 86/2006)

Abstract

73 laboratories received samples for the intercomparison 0620, and 67 laboratories in 26 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 %, 75 % of the overall results were considered as acceptable. The best results were reported for the analytical variables sodium and sulphate, with 88 and 89 % acceptable results, respectively. Lowest percentage of acceptable results was observed for the heavy metals, especially for lead, zinc and nickel, with 52, 61 and 63 % acceptable results. The main reason for these results is the low concentrations of these metals in the samples used. For alkalinity too, there were only 63 % acceptable results. Harmonization of the analytical methods used is necessary to improve the comparability for pH.