Three intercomparison exercises on simulated rainwater were held in th
e period 1991-93 involving 72 to 99 laboratories in Europe and South A
merica. The exercises required the analysis of pH, conductivity, main
anions (Cl-, NO3- and SO42-) and main cations (Ca2+, K+, Mg2+, Na+ and
NH4+). The concentrations of the single ions ranged between 5 and 150
mu mol l(-1). Results were used to evaluate and compare the precision
of the analytical methods. A general improvement in precision was obs
erved in the course of the exercises.