To improve the quality of foliar analysis, the Expert Panel and the FFCC decided to carry out this ringtest annually. Ringtests should not only be a check of the level II data quality, but they should also support the laboratories to get better results before they send the next level II results to PCC. Consequently, the 7th Interlaboratory Comparison Test was started in 2004.
The results of the 7th Interlaboratory Comparison Test show generally a good analytical quality in foliar analysis. Some of the laboratories had to learn from their ringtest results, especially those with outliers type b, c and/or results outside of the tolerable limits. A few of the laboratories must change their methods (e.g. dry ashing!!!) or check their methods with standard reference materials, ring test samples or primary standards.
Calibration Problems of element analysers appear to be corrected. Most of the labs (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-analysers 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, Cu, Pb and Cd.
- Flameless-AAS and ICP-MS methods should be used for analysing Cd, Pb and Cu (especially for low concentrations)
- X-ray fluorescence analyses is the method to generate good results for S, P, Ca, Mg, K, Zn and Mn.