48 laboratories in 23 countries participated in the 20th Needle/Leaf Interlaboratory Test.
A new system for qualification and re-qualification started with the 11th test in 2009. This system was enlarged after the manual update in 2010 to all ICP-Forests partners. With the ring test report, each participant receives a qualification report which can be downloading from the webpage (https://bfw.ac.at/ws/ring_nadel.login). It has been decided to qualify the results of each parameter separately. A laboratory is qualified when 50% or more (generally two, three or all four samples) of the results for this parameter for all the samples of the ring test are within the tolerable limits. Re-qualification is mandatory for all ICP-Forests laboratories if monitoring results (foliage, litterfall, ground vegetation) from the vegetation period 2017 will be submitted to PCC.
The usage of maximum acceptable limits of quantification (LOQ) has been included since the 14th Interlaboratory Test. These limits are needed, because many laboratories are using multi element methods (mostly ICP-AES) with higher LOQs for some elements. But for evaluation and classification of the monitoring samples real measured results and lower LOQ are sometimes needed. The Working Group QA/QC in Laboratories received a task to fix this problem from the Expert Panel Foliage and Litterfall (12th Meeting - Tallinn 2011). Maximum acceptable LOQs for mandatory and optional parameters for foliage, litterfall and ground vegetation were discussed and accepted in the 3rd Meeting of the Heads of the Laboratories (Arcachon 2011). This problem is more or less fixed now for the “old” parameters – only three laboratories submit LOQs higher than the maximum acceptable LOQs (A39: Cd; F07: Mn and F15: Cd). For the “new” parameters (heavy metals) it is not fixed at the moment. The laboratories A39: As, A65: Co, Ni, F05: As, F06: Co, F07: As and F12: Co submit LOQs higher than the maximum acceptable LOQs. Especially for As and Co ICP-MS should be used as determination method to reach these low LOQs.
In case of very low concentrations in the test samples, results of these samples will be excluded from the evaluation (this happened for Pb: samples 2, 3 and 4; Cd: sample 4; As: sample 2; Co: sample 4 and Hg: sample 4). This procedure is needed to avoid wrong qualification results influenced by inaccurate measurements. And on the other hand there is no real need to detect these very low concentrations in real monitoring samples, because it gives no additional information of the nutrient status or of the pollution impact situation.
The following participating laboratories with a percentage of correct results below 80% have severe QC/QA-problems and/or methodical problems:
F21 (79.2%), A45 (78.5%), A43 (75.0%), A56 (75.0%), F09 (75.0%), A88 (71.0%), F24 (64.3%), A83 (63.9%) and A62 (53.6%)
Some of the ICP-Forests laboratories fail and have to do a re-qualification for certain parameters (A45: S, Mn and As; A47: K; A60: S and K; A61: B; A62: Ca, Mg and K; F06: Co; F08: Cu; F09: P and Cu; F21: Ca; F24: Ca; F27: Mg). These (ICP-Forests) laboratories have to check and re-validate their method or employ a better method. FFCC offers old ringtest material if reference material is needed for this purpose (see: http://bfw.ac.at/rz/bfwcms2.web?dok=5146).
The laboratories A59 (K), A62 (Ca, Mg, K), A82 (K) and F09 (P) failed with the same parameter in the last test. Therefore, their QC/QA-problem or their methodical problem is still not solved!
All laboratories are invited to take part in the re-qualification program that starts up from now till 1st of September 2018 (see: http://bfw.ac.at/rz/bfwcms2.web?dok=7830).