Requirements on analytical quality

A general source on requirements for quality is the Eurachem Target Uncertainty guide. Here follows some additional information

From specification

In general the within-lab reproducibility, s(Rw) should be 5 % of the specification or the tolerance according to Measurement System Analysis (MSA); for a specification 100 to 120 and a relatively low bias the s(Rw) should be less than 1.

Environmental sector

EU directive

Drinking water directive 2020/2184/EC  states the required expanded measurement uncertainty for ammonium at the level of 0.5 mg/L to be 40 %. A first estimate of s(Rw) is the required U divided by a factor of 4. Most laboratories will be able to determine ammonium with a relative s(Rw) of 10 % at 0.5 mg/L. The result is the following requirements for s(Rw): 0.05 mg/L or 10 %, whichever is higher. In practice this means that for all concentrations below 0.5 mg/L the required s(Rw) is 0.05 mg/L. From 0.5 mg/L and higher, the requirement is 10 % s(Rw).

Requirement for monitoring 09/90/EC says in Article 4: ... minimum performance criteria for all methods of analysis applied are based on an uncertainty of measurement of 50 % or below (k = 2) ... and a limit of quantification equal or below a value of 30 % of the relevant environmental quality standards. 

GermanY

In the LAWA* – AQS Merkblatt A6/1 2004 is set requirements on s(Rw)

DENMARK

Danish law requirements on expanded uncertainty BEK nr 1146 24/10 2017