Intercomparison 9812. pH, conductivity, alkalinity, nitrate + nitrite, chloride, sulfate, calcium, magnesium, sodium, potassium, total aluminium, reactive and non-labile aluminium, dissolved organic carbon, and chemical oxygen demand (ICP Waters report 49/1998)

Abstract

43 laboratories in 20 countries participated in intercomparison 9812. One sample set for the determination of major ions, organic matter and aluminium fractions, were used. Based on the general target accuracy of * 20 %, 74 % of the results were acceptable. More than 80 % of the result pairs were acceptable for conductivity, nitrate + nitrite, sulfate, sodium, and dissolved organic carbon. For pH only 55 % of the result pairs were acceptable in relation to the extended target accuracy of * 0.2 units. For two analytical variables, reactive and non-labile aluminium, it was decided not to evaluate the reported results, because of the great spread between the results from the few participants. Normalization of the methods is necessary to improve the comparability for these variables. Manual methods are generally less sensitive compared to instrumental methods, and are not always suitable for acid rain monitoring.