Intercomparison 9408. pH, conductivity, alkalinity, nitrate + nitrite, chloride, sulfate, calcium, magnesium, sodium, potassium, total aluminium, dissolved organic carbon, and chemical oxygen demand (ICP Waters report)

26 laboratories in 17 countries participated in intercomparison 9408. Based on the general target accuracy of +-20%, 81% of the results were acceptable. However, for pH only 54% and 59% of the result pairs in the two sample sets were acceptable in relation to the extended target accuracy of +-0.2 units. A total error of +-0.2 units for accuracy of +-0.2 units. A total error of +-0.2 units for pH measurements seems to be reasonable assessment of the accuracy between laboratories. 23 laboratories determined the analytical variables in both the low concentration samples only, and one laboratory analyzed the high concentration samples only. The part of acceptable results are approximately the same for both sample pairs