Intercomparison 9610, 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)
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- NIVA-rapporter 
36 laboratories in 21 countries participated in intercomparison 9610. Two sample sets, one for the major ions and one for organic matter and aluminium fractions, were used. Based on the general target accuracy of + 20%, 70% of the results were acceptable. More than 80% of the result pairs were acceptable for conductivity, nitrate+nitrite, calcium, 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 three analytical variables: alkalinity, reactive and non-labile aluminium, it was decided not to evaluate the reported results, because of the extreme spread of the results between the participants. Normalization of the methods is necessary to improve the comparability for these variables. High concentration of organic anions in sample. A revealed that some laboratories are using methods influenced by interferences, especially for the determination of alkalinity and chloride. Manual methods are generally less sensitive compared to instrumental methods.
PublisherNorsk institutt for vannforskning
ICP Waters report