Intercomparison 1529: pH, Conductivity, Alkalinity, NO3-N, Cl, SO4, Ca, Mg, Na, K, TOC, Al, Fe, Mn, Cd, Pb, Cu, Ni, and Zn

Summary

81 laboratories were invited to participate in the current intercomparison. Of these, 40 from 19 different countries accepted the invitation and 39 of them submitted results to the Organization. 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), 88 % 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: chloride, sulphate, calcium, magnesium, sodium, potassium, cadmium, copper and nickel, with acceptance rate of 90% or higher. For pH, only 64 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. Participants may have observed higher concentrations in the sample set AB if compared to previous intercalibrations. This sample set has been spiked with NaCl, KNO3, NaCl and CaCl2 and MgSO4 salts. The purpose was to compare results for freshwaters with higher content of salts than the naturally occurring in Norwegian lakes and rivers