Intercomparison 1226: pH, Conductivity, Alkalinity, NO3-N, Cl, SO4, Ca, Mg, Na, K, TOC, Al, Fe, Mn, Cd, Pb, Cu, Ni, and Zn (ICP Waters report 111/2012)

Abstract

71 laboratories received samples for the intercomparison 1226, and 68 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 %, 74 % of the overall results were considered acceptable. This is somewhat lower than last years, but in line with the previous ones. The best results were reported for the analytical variables manganese, copper, sodium and cadmium, with 89, 86, 84 and 84 % acceptable results, respectively. The lowest percentage were observed for alkalinity, nitrate, pH and zinc with 48, 52, 59 and 61 % acceptable results. Nitrate showed clear sign of not being sufficiently stable during the period of analysis. Harmonization of the analytical methods used, and the practical procedures followed, may be the most important way to improve the comparability for these parameters.