Lassen, P. & Larsen, M.M. 2021. Report on the HELCOM PLC-8 intercalibration. Aarhus University, DCE – Danish Centre for Environment and Energy,128 pp. Technical Report No. 212. http://dce2.au.dk/pub/TR212.pdf
The number of participating laboratories is shown in table 5.1.
Only a few laboratories have reported below DL/QL for Pb and Zn in freshwater, see table 5.2. In the PLC-8 intercalibration, all samples have been spiked in order to secure concentration levels at minimum 10 times the recommended detection limits from HELCOM.
A summary of the results from the PLC-8 intercalibration is shown in table 5.2 for freshwater and 5.3 for waste water.
The recovery of Zn is not calculated as the recovery was high above 100% and it is concluded that there must have been an error in the spiking.
In general, the analytical quality is good and comparable between the laboratories with a few exceptions. For both freshwater and waste water, all components have low deviation, though Hg has a bit higher deviation in waste water and for freshwater and the recovery of Cd is a bit too low.
For NO2-N in waste water (table 5.3), the samples were clearly unstable and cannot be used for the evaluation of the laboratories. The expected value based on the spiking was 0.8 mg/L, but the laboratories reported data in the range from 0.004-0.44 mg/L. The same was not the case for freshwater. For the freshwater, the average for the A/B samples from the laboratories was near the expected value based on the spiking at 0.25 mg/L. It is unclear what caused this instability in the waste water samples.
For comparison in relation to the analytical quality, the requirements in Danish Statutory Order no 1071 of 28/10/2019 on the analytical quality for environmental measurements from Ministry of Environment are shown in table 5.4.
It is not possible to directly compare table 5.2 and 5.3 with table 5.4 as data in table 5.2 and 5.3 are calculated across the laboratories, whereas table 5.4 shows requirements within each laboratory. However, the deviations in the intercalibration are in the same range as the requirements in Danish Statutory Order, indicating that the monitoring results in overall are reliable.
