PRECISION OF ION-CHROMATOGRAPHIC ANALYSES COMPARED WITH THAT OF OTHERANALYTICAL TECHNIQUES THROUGH INTERCOMPARISON EXERCISES

Three intercomparison exercises on simulated rainwater were held in 19 91-1993 involving 72-98 laboratories in Europe and South America. Ion chromatography was used for the determination of anions (chloride, nit rate and sulphate) by 59-72% of the participating laboratories and for the determination of cations (Na,K, Mg and Ca) by 14-22% of them. The concentration of the single ions ranged between 5 and 150 mu mol l(-1 ). The results were used to evaluate the precision of the method, and showed that it was comparable to that of spectrophotometric methods. F or ammonium ion, ion chromatography was used by only 4-14% of the labo ratories and the results depended on the calibration technique adopted . A general improvement in precision was observed in the course of the exercises.