Requirements on analytical quality
A general source on requirements for quality is the Eurachem Target Uncertainty guide. Here follows some additional information
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.
Drinking water directive 98/83/EC set requirement on trueness (bias) and 2s(Rw) in section 2 of appendix II. For e.g. ammonia at a level of 0.5 mg/l the requirement on bias is < 10 % and 2s(Rw) is 10 %
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.
In the LAWA* – AQS Merkblatt A6/1 2004 is set requirements on s(Rw)
Danish law requirements on expanded uncertainty BEK nr 1146 24/10 2017