Intercomparison 9509. 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)

Abstract

46 laboratories in 21 countries participated in intercomparison 9509. 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 %, 72 % of the results were acceptable. For pH, less than 50 % of the result pairs were acceptable in relation to a target accuracy of + 0.1 units, and 73 % 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. In the future a sample set with more suitable concentration for alkalinity has to be ussed. To improve the comparability for the determination of aluminium fractions, it is necessary to normalize the analytical method to be used. Manual methods are generally less sensitivecompared to instrumental methods, and may be less suited for typical acid precipitation samples.