Intercalibration 9206. pH, conductivity, alkalinity, nitrat + nitrite, chloride, sulfate, calium, magnesium, sodium, potassium, aluminium and dissolved organic carbon (ICP Waters report)

23 laboratories in 18 countries participated in intercalibration 9206. Based on the general target accuracy of ± 20 %, about 80 - 90 % of the results were acceptable for the main components. However, for pH only 30 and 70 % of the result pairs in the two sample sets were acceptable in relation to the target accuracy of ± 0,1 units. Supersaturation with carbondioxide is probably the reason why we observe reduced quality of pH data in circumnneutral samples