Intercomparison 1327: pH, Conductivity, Alkalinity, NO3-N, Cl, SO4, Ca, Mg, Na, K, TOC, Al, Fe, Mn, Cd, Pb, Cu, Ni, and Zn (ICP Waters report 116/2013)

In the current ICP Waters Intercomparison program, 106 laboratories were invited to participate. 66 accepted the invitation and 60 laboratories from 28 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 %, 76 % of the overall results were considered acceptable. This is slightly better than last year, but in line with previous editions. The best results were reported for the analytical variables sodium, calcium, aluminium, cadmium, copper and nickel with 91, 85, 89, 85, 84 and 83 % acceptable results respectively. The lowest percentage of acceptable results was observed for pH and Zn, where only a 52 and 60 % of the reported results were acceptable respectively. The improvement of quality in the determination of alkalinity in the current edition is noteworthy, with 63% of acceptable results compared to the previous one with only 48 %. Nitrate showed clear signs of not being sufficiently stable and extremely different results were reported from participants. Harmonization of the analytical methods used and of the practical procedures followed, may be the most important way to improve the comparability for these parameters.Norwegian Environmental AgencyUnited Nations Economic Commission for Europe (UNECE