Contribution to the certification of B, Cd, Mg, Pb, Rb, Sr, and U in a natural water sample for the International Measurement Evaluation Programme Round 9 (IMEP-9) using ID ICP MS

The present paper describes the contribution of the Institute for Reference Materials and Measurements to the certification of B, Cd, Mg, Pb, Rb, Sr, and U amount contents in a natural water sample, in round 9 of the Internat ional Measurement Evaluation Programme (IMEP-9). The analytical procedure t o establish the reference values for B, Cd, Mg, Pb, Rb, Sr, and U amount co ntents was based on isotope dilution inductively coupled plasma-mass spectr ometry used as a primary method of measurement. Applying this procedure ref erence values, traceable to the SI, were obtained for the natural water sam ple of IMEP-9. For each of the certified amount contents presented here a t otal uncertainty budget was calculated using the method of propagation of u ncertainties according to ISO and EURACHEM guidelines. The measurement proc edures, as well as the uncertainty calculations are described for all seven elements mentioned above. In order to keep the whole certification process transparent and so traceable, the preparations of various reagents and mat erials as well as the sample treatment and blending, the measurements thems elves, and finally the data treatment are described in detail. Explanations focus on Pb as a representative example. The total uncertainties (relative ) obtained were less than 2% for all investigated elements at amount conten ts in the pmol/kg up to the high mu mol/kg range, corresponding to low mu g /kg and mg/kg levels.