contaminants in  marine water interlaboratory testing

High and low salinity seawater, estuarine water and freshwater

Proficiency tests

Participation is open to all laboratories.

Determinand Group Sample Type Exercise
Nutrients (e.g. NO2 and PO4) High salinity seawater AQ1
Nutrients (e.g. NO2 and PO4) Estuarine and low salinity seawater AQ2
Metals (e.g. Cd, Cu and Zn) High and low salinity seawater AQ3
Mercury High and low salinity seawater AQ4
Halogenated organics (e.g. OP-DDT, CB153) High and low salinity seawater AQ5
Volatile organics (e.g. benzene, toluene) High salinity seawater AQ6
Pentachlorophenol High salinity seawater AQ7
Pesticides (e.g. atrazine, chlorpyrifos) High and low salinity seawater AQ8
Chlorophyll and Pheopigments Estuarine and fresh water AQ11
Organotins (e.g. TBT and TPhT) High salinity seawater AQ12
PAHs (e.g. Anthracene and Chrysene) High and low salinity seawater AQ13
DOC High and estuarine seawater AQ14
Ocean acidification (total alkalinity, DIC and pH) High and low salinity seawater AQ15
Polar/nonpolar compounds Sampler(s) DE13
PFAS (Sea)water DE18
Pharmaceuticals (Sea)water DE19

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General information

  • Seawater samples are mainly prepared from seawater originating from the North Sea, Atlantic Ocean, the Baltic sea and estuarine water to cover water samples with varying salinity. For chlorophyll samples sometimes freshwater samples are used.
  • Water samples are filtered using a 0.45µm / 0.2µm double membrane filter.
  • The water samples are stable for the period of the test when stored properly.
  • All seawater samples are prepared in bulk and tested for its homogeneity where relevant.
  • Use your normal validated methods and procedures to analyse the test materials.
  • Some of the PT samples (AQ5; AQ7; AQ8; AQ12 and AQ13) need to be spiked in your own laboratory because of stability issues.
  • New determinands can be added to these programs on request.
  • Reports contain all data reported under strict confidentiality, including Z-score plots and method information of methods used.


Samples of previous proficiency tests are sold as reference materials. Available materials can be selected and ordered in our webshop. Participants of our proficiency tests are entitled to a discount.