Intercomparison 1630: pH, Conductivity, Alkalinity, NO3-N, Cl, SO4, Ca, Mg, Na, K, TOC, Al, Fe, Mn, Cd, Pb, Cu, Ni and Zn

89 laboratories were invited to participate in the current intercomparison. Of these, 35 from 20 different countries accepted the invitation and all of them submitted results to the ICP Waters. Two sample sets were prepared: one for the determination of major ions and one for heavy metals. Based on the general target accuracy of ± 20% or the special accuracy limit for pH and conductivity (± 0.2 pH units and ± 10% respectively), 81% of the overall results were considered acceptable. This is in line with previous editions. The best results were reported for the analytical variables: sulphate, calcium, sodium, iron, manganese, cadmium and nickel with acceptance rate of 90% or higher. For pH, only 56 percent of the reported results fulfilled the acceptance criteria. 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.