Due to the retirement of Mr. Bartels from the Foliar Expert Panel, the Forest Foliar Coordinating Centre indicated its willingness to organise the 6th Interlaboratory Comparison Test at the 8th Expert Panel Meeting in Prague (28-29th April 2003 ). The Panel proposed the following timetable:
- Informing the participating labs and preparation of the web-page (6th May 2003)
- Registration of the labs via Internet (till 30th June 2003)
- Submission of the test samples (End of July 2003)
- Input and recheck of the analysis results from the labs (September-December 2003)
- Deadline of data input and recheck (31th of December 2003)
- Evaluation according to DIN 38402 (January/February 2004)
At the end of July the Forest Foliar Coordinating Centre sent four dried and powdered plant samples to 45 European laboratories in 26 countries. For each element four replicates per sample are necessary within this Interlaboratory-Test.
The mandatory parameters S, N, P, K, Ca, Mg must be analysed, optional parameters Zn, Mn, Fe, Cu, Pb, Cd, B and C can be analysed and some additional elements are possible.
The results of the 6th Interlaboratory comparison test show generally a good analytical quality in foliar analysis. Few of the laboratories had to learn from their ringtest results, especially laboratories with outliers and/or results outside of the tolerable limits. A few of the laboratories must change their methods (e.g. dry ashing!!!). Some laboratories sent also detection limits, but a few of these detection limits were sent in wrong units.
Good equipment is not only necessary for acceptable results, but also a well educated staff is a basis for good results. The use of control charts, reference materials and/or primary standards should be a daily quality routine. Till now approximately 90% of the participating labs are using quality control charts (70% of the labs are using average charts). More than 50% of the laboratories are already accredited or plan the accreditation within 1-2 years.
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 methods for Cd, Pb and Cu (especially for low concentrations)
- X-ray fluorescence analyses for S, P, Ca, Mg, K, Zn and Mn.