The results of the 9th Interlaboratory Comparison Test show generally a good analytical quality in foliar analysis. Especially the results of the mandatory elements (N, S, P, Ca, Mg and K) are quite good and better than in the tests before. Some of the laboratories had to learn from their ringtest results and had to improve their quality. They had to make a revision of their method, especially those with statistic outliers and/or results outside of the tolerable limits (laboratories 30, 23 and 74). A few laboratories must change their methods completely (e.g. dry ashing, nephelometry determination of sulphur), because these methods are not recommended and not state of the art. Calibration problems with element analysers are back again. Most of the labs (close to 90%) are using control charts as a daily routine procedure. A trend in the use of analytical methods can be seen:For C, N, (S) element-analyzers are becoming more and more important. .. Acid digestion methods in closed systems in combination with ICP methods are very good for the determination of S, P, K, Ca, Mg, Fe, Zn, B and Cu. .. Flameless-AAS and ICP-MS methods should be used for analysing Cd, Pb and Cu (especially for low concentrations) .. An X-ray fluorescence analysis is the method to generate good results for S, Ca, Mg, K, Zn and Mn, but X-Ray analyzers show for the spruce samples in this interlaboratory test higher phosphorous results.
