# Commission Decision of 12 August 2002 implementing Council Directive 96/23/EC concerning the performance of analytical methods and the interpretation of results (notified under document number C(2002) 3044) (Text with EEA relevance) (2002/657/EC), Division 2.3.2.2: Precision of quantitative methods

Extent: E+W+S+N.I.

The inter-laboratory coefficient of variation (CV) for the repeated analysis of a reference or fortified material, under reproducibility conditions, shall not exceed the level calculated by the Horwitz Equation. The equation is:
CV = 2 ( 1 – 0 , 5 l o g C ) where C is the mass fraction expressed as a power (exponent) of 10 (e.g. 1 mg/g = 10-3). Examples are shown in the table 3.
Table 3
Examples for reproducibility CVs for quantitative methods at a range of analyte mass fractions
Mass fraction
Reproducibility CV(%)
(*) For mass fractions lower than 100 μg/kg the application of the Horwitz Equation gives unacceptable high values. Therefore, the CVs for concentrations lower than 100 μg/kg shall be as low as possible.
1 μg/kg
10 μg/kg
100 μg/kg
23
1 000 μg/kg (1 mg/kg)
16
For analyses carried out under repeatability conditions, the intra-laboratory CV would typically be between one half and two thirds of the above values. For analyses carried out under within-laboratory reproducibility conditions, the within-laboratory CV shall not be greater than the reproducibility CV.
In the case of substances with an established permitted limit, the method shall achieve within-laboratory reproducibility not greater than the corresponding reproducibility CV at a concentration of 0,5 × the permitted limit.

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Source: https://www.legislation.gov.uk/eudn/2002/657/annex/chapter/2.3/division/2.3.2.2 (the official version)
Page: https://openlegislation.uk/eu-decision-2002-657/annex/chapter-2.3/division-2.3.2.2
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.