Commission Directive 2005/10/EC (repealed)Show full title

4. Method of analysis to be used by the laboratory and laboratory control requirements

4.1. Definitions

A number of the most commonly used definitions that the laboratory will be required to use are given below:

r

=

Repeatability, the value below which the absolute difference between two single test results obtained under repeatability conditions (i.e., same sample, same operator, same apparatus, same laboratory, and short interval of time) may be expected to lie within a specific probability (typically 95 %) and hence .

s_r

=

Standard deviation, calculated from results generated under repeatability conditions.

RSD_r

=

Relative standard deviation, calculated from results generated under repeatability conditions .

R

=

Reproducibility, the value below which the absolute difference between single test results obtained under reproducibility conditions (i.e., on identical material obtained by operators in different laboratories, using the standardised test method), may be expected to lie within a certain probability (typically 95 %); .

s_R

=

Standard deviation, calculated from results under reproducibility conditions.

RSD_R

=

Relative standard deviation calculated from results generated under reproducibility conditions , where is the average of results over all laboratories and samples.

HORRAT_r

=

the observed RSD_r divided by the RSD_r value estimated from the Horwitz equation (1) using the assumption r = 0.66R.

HORRAT_R

=

the observed RSD_R value divided by the RSD_R value calculated from the Horwitz equation.

U

=

the expanded uncertainty, using a coverage factor of 2 which gives a level of confidence of approximately 95 %.

4.2. General requirements

Methods of analysis used for food control purposes must comply with points 1 and 2 of the Annex to Council Directive 85/591/EEC.

4.3. Specific requirements

Where no specific methods for the determination of benzo(a)pyrene in food are prescribed at Community level, laboratories may select any validated method provided the selected method meets the performance criteria indicated in the Table. The validation should ideally include a certified reference material.

TABLE

Performance criteria for methods of analysis for benzo(a)pyrene

Parameter	Value/comment
Applicability	Food specified in Regulation (EC) No …/2005
Detection limit	No more than 0,3 μg/kg
Limit of quantification	No more than 0,9 μg/kg
Precision	HORRATr or HORRATR values of less than 1.5 in the validation collaborative trial
Recovery	50 %-120 %
Specificity	Free from matrix or spectral interferences, verification of positive detection

4.3.1. Performance Criteria — Uncertainty Function Approach

However, an uncertainty approach may also be used to assess the suitability of the method of analysis to be used by the laboratory. The laboratory may use a method which will produce results within a maximum standard uncertainty. The maximum standard uncertainty can be calculated using the following formula:

where:

Uf

is the maximum standard uncertainty

LOD

is the limit of detection of the method

C

is the concentration of interest

If an analytical method provides results with uncertainty measurements less than the maximum standard uncertainty the method will be equally suitable to one which meets the performance characteristics given in the Table.

4.4. Recovery calculation and reporting of results

The analytical result is to be reported corrected or uncorrected for recovery. The manner of reporting and the level of recovery must be reported. The analytical result corrected for recovery is used for checking compliance (see Annex I, point 5).

The analyst should note the ‘European Commission Report on the relationship between analytical results, the measurement of uncertainty, recovery factors and the provisions in EU food legislation’ (2).

The analytical result has to be reported as x +/– U whereby x is the analytical result and U is the measurement uncertainty.

4.5. Laboratory quality standards

Laboratories must comply with Directive 93/99/EEC.

4.6. Other considerations for the analysis

Proficiency testing

Participation in appropriate proficiency testing schemes which comply with the ‘International Harmonised Protocol for the Proficiency Testing of (Chemical) Analytical Laboratories’ (3) developed under the auspices of IUPAC/ISO/AOAC.

Internal quality control

Laboratories should be able to demonstrate that they have internal quality control procedures in place. Examples of these are the ‘ISO/AOAC/IUPAC Guidelines on Internal Quality Control in Analytical Chemistry Laboratories’ (4).