Intercomparison 2236: pH, Conductivity, Alkalinity, NO3-N, Cl, SO3, Ca, Mg, Na, K, TOC, Tot-P, Tot-N, Al, Fe, Mn, Cd, Pb, Cu, Ni, and Zn.

Summary

Twenty-six laboratories from 15 countries accepted the invitation to join the ICP Waters chemical intercomparison and twenty-three of these successfully reported their results. Two sets of samples were prepared and distributed to the participants: one for the determination of ions and one for metals. In general, the results were of the same quality as previous years, with an overall acceptance rate of 75% (± 20% of the “true value”, and for pH and conductivity ± 0.2 pH units and ± 10%, respectively). The highest acceptance rates (≥ 90%) were obtained for aluminium, iron and chloride. The lowest acceptance rates were for total phosphorous and total nitrogen, at 33%. Total nitrogen was included for the first time this year. General trends in the choice of techniques continue to shift towards plasma from atomic absorption, and to mass detection from ionic emission. This is especially promising for the determination of metals at low levels.