Intercomparison 0014: pH, Cond, HCO3, NO3+ NO2, Cl, SO4,Ca, Mg, Na, K, total-aluminium, aluminium - reactive and nonlabile, DOC, COD-Mn, Fe, Mn, Cd, Pb, Cu, Ni and Zn (ICP Waters report 55/2000)

Abstract

71 laboratories received samples for the intercomparison 0014, and 65 laboratories in 26 countries submitted results. Three sample sets were used, one for the determination of major ions, one for organic matter and aluminium fractions, and one for heavy metals. Based on the general target accuracy of ± 20%, 63% of the results were considered acceptable. About 90% of the results pairs were acceptable for sodium and dissolved organic carbon. For pH only 57% of the result pairs were acceptable i relation to the extended target accuracy of ± 0.2 units. For nitrate + nitrite it was decided not to evaluate the reported results, because of the instability of this analytical variable in the samples A and B. Determination of heavy metals was included in the intercomparison for the first time, with fairly good results for iron and manganese. For lead, nickel and zinc where less than 50% of the results were acceptable, may be due to the low concentrations used for these metals. Normalization of the analytical methods used is necessary to improve the comparability for pH. For the heavy metals it should be discussed whether an absolute acceptance limit should be used instead of the general target of ± 20% when the concentrations are close to the detection limit of the recommended method.