Commission Regulation (EC) No 273/2008 (repealed)Show full title

EVALUATION OF COMPLIANCE OF A CONSIGNMENT WITH THE LEGAL LIMIT

1. PRINCIPLE

In cases where detailed sampling procedures are given by the relevant legislation, these procedures are followed. In all other cases a sample of at least 3 sample units taken randomly from the consignment submitted to control is used. A composite sample may be prepared. The result obtained is compared with the legal limits by calculation of a 95 % confidence interval as 2 x standard deviation, where the relevant standard deviation depends on whether (1) the method is validated through international collaboration with values for σr and σ_R or (2) in the case of in-house validation, an internal reproducibility has been calculated. This confidence interval will then equate to the measurement uncertainty of the result.

2. THE METHOD IS VALIDATED THROUGH INTERNATIONAL COLLABORATION

In this case the repeatability standard deviation σr and the reproducibility standard deviation σ_R have been established and the laboratory can demonstrate compliance with the performance characteristics of the validated method.

Calculate the arithmetic mean of the n repeated measurements.

Calculate the expanded uncertainty (k = 2) of as

If the final result x of measurement is calculated using a formula of the form x = y ₁ + y ₂, x = y ₁ – y ₂, x = y ₁ · y ₂ or x = y ₁ / y ₂ the usual procedures for combining standard deviations in such cases must be followed.

The consignment is judged to be not in compliance with the upper legal limit UL if

;

otherwise it is judged to be in compliance with UL.

The consignment is judged to be not in compliance with the lower legal limit LL if

;

otherwise it is judged to be in compliance with LL.

3. IN-HOUSE VALIDATION WITH CALCULATION OF INTERNAL REPRODUCIBILITY STANDARD DEVIATION

In cases where methods not specified in this Regulation are used and precision measures have not been established an in-house validation must be carried out. Internal repeatability standard deviation s_ir and the internal reproducibility standard deviation s_iR have to be used instead of σ_r and σ _R , resp., in the formulae for the computation of the expanded uncertainty U.

The decision rules are as under (1). However, if the consignment is judged to be not in compliance with the legal limit the measurements must be repeated with the method specified in this Regulation and the decision reached according to (1).